Eartha Kitt's first appearance in "Timbuktu!," the splashy musical now at the Kennedy Center, is not just an entrance. It is designed as a flamboyant event worthy of the great Ziegfeld.

She is standing, literally, on the palms of a giant in loincloth, his forearms horizontal at elbow level. The bearer stops at center stage, which is crowded with exotic figures in similar economy of dress, and lowers Kitt to the floor. She pauses with an expression appropriate to Princess Sahleem-la-Lume, the power behind the throane of Timbuktu in the year 1361.

When all eyes are finally on her, she declares in that unmistakable huskiness: "I am here."

"All Timbuktu rejoices at you!" the throng responds.

A long pause. Then Kitt snaps capriciously, "Anything new in town?"

The audience breaks up. Kitt has caught then by surprise - and they are suddenly conscious that Kitt herself has been away as well as La-Lume.

The production number carries all the trappings ofstardom, which is something that Ertha Kitt has not experienced on the stage of an American theatre in a long time.

Her's is a story of the perils of fame. It is about the difficulties of coping, in quick session, with childhood of poverty in the rural South; of being abandoned by her mother at 9; of being tagged "the most exciting woman in the world" by Orson Wells in her early 20s, of a triumphant Broadway debuck at 24; and being the toast of Paris cafe society in the 1950s, hobnobbing with the likes of Porfirio Rubirosa and Jawaharal Nehru.

But for the past decade, Kitt has*suffered what she regards as a social ostracism traceabl*e to her antiwar remarks at a 1968 White House luncheon *and the publicity that followed.

Kitt sees what happened to her in fairly simple terms. Discussing it recently over breakfast, she said, "After that White House thing the government just pulled the gate on me. It was just years later before I knew what happened. But I knew something was happening. Dates simply started getting canceled. I knew that some government investigators had come around checking. I didn't know what it was for, then. But in those days you didn't need any more than for the FBI to come in and ask about your personality to damage you. One club owner told me he was sorry, but, 'You're a problem.'"

Even when discussing the White House incident, Kitt seems subdued by comparison with the tart, feline stage persona she has cultivated or the anger she has occasionally shown in public statements. The voice is softer. There is a mix of cautious warmth, toughness, naive vanity and, when certain subjects are broached, evasiveness.

Kitt's confrontation with President Johnson came when he made a surprise appearance at a Woman Doers' luncheon given by the First Lady. Kitt was one of 50 women guests invited to discuss the subject, "Why is there so much juvenile delinquency in the streets of the United States?"

When the president finished his speech, which Kitt felt ignored the central issue she accosted him, acting on one of those impulses, recurring throught her life, in which she plunges without pondering the implications. "Mrs. Johnson's account had me blocking the path between the podium and the door. I don't recall that, but I was certainly angry enough."

She questioned a suggestion by the President that "combating crime starts in the home." Kitt, who is active in ghetto youth projects, addressed him "Mr. President, what are we to do with parents who are delinquent?" and continued in that mode as he walked toward the door.

Later in the luncheon, Kitt was reported to have told the First Lady, "You send the best of this country off to be shot and maimed . . . They rebel in the street.They will take pot . . . and they will get high. They don't want to got to school because they're going to matched off from their mothers to be shot in Vietnam.

Kitt says now that history has vindicated her statement. Asked if she would do it again, she snaps back, "I don't think there is anything I have done that I wish I hadn't done. Because I learn from everything I do. I'm in school every day. My diploma will be my tombstone."

It was not, however, until 1975 that Kitt learned through newspaper reports that an upshot of that incident was the assembling of a Secret Service dossier filled with gossip about her personal life, but concluding she was no immeadiate threat to the Republic. A CIA document quoted a 1956 source in Paris as saying Kitt had "a lurid sex life" and describing her as "a sadistic nymphomaniac."

Kitt replied, "I have always lived in very clean life. I have nothing to be afraid of, and I have nothing to hide."

Whether the White House incident was an important factor or not, Kitt's career as a star had been slipping for several years. And when the eclipse came, it seemed total. Until "Timbuktu!" her last important American stage role was in the road show of "The Owl and the pussycat" in 1966.

She had been at the top for well over a decade, starting in the early 1950s. Then she was dropped by clubs where she had been a leading attration ("I did the Plaza's Persian Room seven straight years in a row." The television quiz show on which she had been a regular did not invite her back. Recordings stopped.There were no more "C'est Si Bon's" or "I Want to Be Evil's." The last big film role was in 1965.

Though she kept her home in California, she went abroad to make her living. There were two plays in London, and numerous night club appearance in Europe, Asia and - to the raised eyebrows of some - South Africa.

The longer she was out of the public eye in this country, the greater the odds became that she might never return. As she writes in 1976 in "Alone With Me," her second autobiographical book, "Few can afford to simply drop out of sight for seven years without being considered a has-been in the entertainment industry . . . some would believe I retired." And on top of that, they were probably the best years of my career," Kitt, who will be 50 this month, says now.

Things began to improve a bit in 1974, with her first American club dates in years. And it was at an appearance the following year at the Persian Room that director Geoffrey Holder, then riding high on the success of the "The Wiz," came back after a performance and told her, "For heaven's sake, you should be on the stage."

But another year passed before she was invited back. Holder called her one day at home and asked her to be in an all-black revision of "Kismet," reset in Timbuktu.

La-Lume, a lesser role in the original, was to be expanded inta a central character. She would have a new song as well as sing more of the original music. The musical was aiming to be a big hit, at a cost of about $1 million.

At the opening of "Timbuktu's" pre-Broadway run here Saturday, most critics praised Kitt's La-Lume. The show is doing a brisk business at the box office, and, at least one night last week, there was a cascade of "bravos" for Kitt at the conclusion.

The opening here also coincided with her performance of a fairly substantial part in a segment of "Police Woman": "I did a prostitute crusading against a politician for the civil rights cause. I admired the character I was playing."

It is clear that Kitt never stopped thinking of herself as a star and in "Timbuktu!" she gets top billing over Melba Moore, who swept the Broadway awards sweepstakes for "Purlie," and Gilbert Chase, who made his name in "Lost in the Stars" and "The Night That Made America Famous."

My public didn't want me to give up, Kitt says. "You know, both myself and my public have been cheated. They didn't get to see me. The public didn't forget me.

"It's because I'm not a faker. I honestly love my public. It's something you can't fake."

She categotized herself, when asked, as an "international continental personality." She recollects that the head of a hotel chain in the Far East remarked her, "Now that Josephine Baker is gone and Marlene is inactive, you're the last one left. You don't belong to anybody, you beling to the world."

One public image that she emphatically renounces is that of the martyr to a cause. "I think theevils of life should be fought, but I am not a crusader. I have a sense of humor and crusaders don't. Neither am I a political person. I belong to no clubs or organizations. I'm a loner."

The word "loner" is a recurring one both in her conversations and in her writings. Long before the career crisis, hers had been a very hard life.

"There were times when I was totally isolated from everybody, including my family, even my daughter, Kitt." "Alone With Me" is dedicated to Kitt, now 16, "who has made me realize what a human being really is all about."

The daughter was born during her mother's marriage to William McDonald, a California real estate man. Obviously a troubling memory for her, Eartha Kitt observes in the book, "To avoid raising unanswered questions, I'll add that my ex-husband was a student when I met him, and he's white. One marriage was going to last forever, but like more than half the marriages in this country today, it didn't."

Her home was the community of North, S.C., and she was born into poverty. Her mother was a field worker, and her father was a white man who, according to Kitt, married here mother after she was born.

The mother abandoned her before she was 9, and she was left to live with another family. At 10 she went to Harlem to live with an aunt who, for reasons she still does not understand, eventually rejected her. By 14, she was living in the subways or at the homes of friends.

Then began the rise to stardom. She was accepted as a dancer with Katherine Dunham's famous troupe. There was a European tour. She was discovered by a Paris nightclub owner. And in turn was chosen by Orson Welles to play Helen of Troy in a European production of "Dr. Faunt."

At the same time she fell in with the international glamour set, with people like Porfirio Rubirosa, who is one of the 64 persons (both friend and foe to whom she dedicated "Alone With Me." The dedications are jucier than much of the book).

The inscription is a "Rubirosa, who wooed me [platonically] and spoiled me with Dom Perignon and caviar." The range of names is wide. There are, for instance, "Prime Minister Nehru, who served me chicken a la king instead of an Indian dinner"; or, "Lady Bird Johnson, who made me remember that not all who ask questions seek truth"; or, "All my lovers, who walked away when they couldn't handle it"; and, finally, "Me, who has learned that intelligence and sex are a difficult combination to handle."

Five years after Dunham took her from Harlem, she made her Broadway debut as the bored vamp singing "Monotonus" in "New Faces of 1952," which brought her international celebrity.

It also brought an identity problem that she says she has never entirely overcome, and one she thinks has made here vulnerable to mistakes and misjudgments. She writes that she has never been entirely able to reconcile the "Ertha Mae of her childhood: 'ugly, unloved, unworthy,'" with "Eartha Kitt; self-reliant, afraid of nothing, even defiant." Apparent contridictions in behavior hav ensued.

Perhaps one example is her tour of South Africa and Rhodesia as an "honorary white" in the spring of 1972, and event which is not mentioned in the book. During those seven weeks she lived in white-only hotels and rode in white-only elevators. She recalls one snub. She was asked to leave an amusement park where she had taken her daughter, who was not asked to leave. But the following day she received flowers and an apology from the manager.

Kitt points out now that she helped pay for a 12-room school for South African blacks and that she spent many hours touring the run-down "colored" sections.

There is a striking consistency about Kitt, one apparent in her conservation and in her writing. She describes her life as a success story, in which disaster, for a citizen of the world, has been only a temporary setback.

"I don't carry myself as a black person," she declares. "I am a world person. I have tremendous curiosity, and I believe in first-hand knowledge. And I probably know more about South Africa than the politicians."