It was 10 a.m., and a weary Billy Carter sat among friends at a large table in the dining room of the Best Western Motel, a half-empty bottle of beer before him, a cigarette in his trembling hand.

The scene was a familiar one here, but many of those who know Billy say a change has come over him of late, that the clowning has given way to brooding, that there is a different Billy Carter.

Signs of strain were everywhere apparent. Seldom seen in public without a drink in hand, he chainsmokes five packs of cigarettes a day, and the jokes fall between uncomfortable periods of silence.

Friday Billy was admitted to Sumter County Hospital with a fever, breathing difficulties, and trembling -- "bronchitis," said his physician and close friend, Paul C. Broun.

"He shakes from anxiety, and just the pressure he's been under -- all the bad press and all the hassle with the Bert Lance thing -- have gotten the guy really uptight. Anyone as anxious as he is, shakes," Broun said. Carter spent the day resting in a private room, with only family members permitted to visit. He was listed in "good condition" yesterday. Only 10 months before he had been admitted for exhaustion, Broun said.

Broun said there was no truth to rumors that Billy had been admitted for alcohol-related problems. "He's able to handle his alcohol very well, and I don't see any problems with it," Broun said.

Many of Carter's friends had seen the illness coming for some time.

"He's been through an awful lot. The boy's tired," said one Carter confidant who asked not to be identified. He said Carter was exhausted from the personal, financial and public travails he had recently under-gone.

Everywhere Billy goes, there is the press, asking him to explain his finances and to account for Justice Department investigations into his business and personal dealings.

"It's changed Billy. Billy has always been a very humorous person. He's become a serious Billy Carter trying to answer these allegations," said Best Western owner Jimmy Murray, one of Billy's closest friends.

At the approach of a reporter in the motel dining room the other day, Billy's friends closed ranks around him as though to protect him. They cautioned Billy that the reporter would only "twist your words," that he was interested only in extracting another outrageous statement to embarrass his brother, the president.

But Billy, as usual, consented to an interview. On this occasion he left the table and followed the reporter into a dimly lit banquet room, and began pacing the room nervously, puffing his cigarette and searching for an ashtray. It was hard to believe this was the same man who, only a few years earlier, had taken such relish in interviews.

It has not been a good period for Billy. His wife, Sybil, had been in an Atlanta hospital last week with phlebitis, and had been released Thursday. The concern showed on Billy's face.

Billy spent much of the past week in an Atlanta motel, leaving to visit his wife in the hospital twice a day, and returning to nap in the motel room. "He was only up for a couple of hours a day. He's got a respiratory problem or something he can't shake," one of Carter's friends said.

Nor has business been good for Billy. The once-lucrative speaking engagements are over. "You know as well as anybody, I blew that," Billy said. A short-lived interest in The Plains Statesman, the local newspaper, collapsed after an alleged fallingout with his partner. "Billy Beer" has gone flat.

The escorting of a Libyan entourage in January has brought him under Justice Department scrutiny for possible violations of foreign agent registration requirements. "I'm not a foreign agent," insisted Billy, saying he would not register as such. "Nobody else does."

Even the Carter Warehouse, which had reportedly prospered under his stewardship, is under a cloud of federal investigation, and his personal and warehouse records are being looked at for possible campaign, banking and tax violations. "I'm getting sick of rumors from the grand jury," Billy snapped.

"Not one penny" from bank loans for the warehouse went to finance his brother's campaign, Billy told a reporter. But it was Billy's wife, Sybil, who kept the books, and Billy simply doesn't understand them. according to a Treasury Depertment source. "Every time he tries to answer a question, he raises more," the source said.

Billy claims he is the incidental victim of an investigation into the finances and business practices of former budget director and Georgia banker Bert Lance. "They couldn't find a damn thing wrong with him, so they had to find someone else," Billy steamed.

In the tiny south Georgia town of Plains (population under 700) and environs, the news of a federal investigation has also taken its toll on Billy's six children. "It bothers the hell out of my kids. They catch a lot of flak at school," Billy said.

Those already isolated from Billy have drawn back even further. "I don't want to be involved with Billy and them. We have always been very distant in our businesses," said first cousin Hugh Carter, a Georgia state senator.

There have even been a number of threats on Billy's life, as well as threats to his family, according to Jimmy Murray, who said Billy sometimes goes to an undisclosed "hideaway."

Randy Coleman a Billy crony, who, like all Billy cronies, is fiercely loyal, says he is not a bodyguard to Billy, despite reporters' impressions to the contrary. "Billy has always refused protection," Coleman said.

Billy's friends denied that he has a drinking problem, though their estimates of his laily consumption vary widely.

Murray insists that Billy's drinking has never gotten out of hand, that it is grossly exaggerated by the press, and that "like you or me" he gets drunk on occasion, but is usually alert and sober.

Another Billy friend said Billy drinks about a six-pack a day. "If Billy has a drinking problem, I do, because I'm always with him and I know I don't," he said.

"If a doctor told him to stop, he could," Coleman declared. "I couldn't say he's sober, but you don't see him drunk, either. Billy has nothing else to do. It's a pastime."

Coleman, like Murray, upbraids the press for distorting the image of Billy, and says reporters see him only "at the filling station or on the road. They don't see him at home. They catch him only at cocktail conveniences."

Coleman depicts a Billy Carter few reporters know, a quiet man who prizes what corner of privacy remains for him, a man who rises at 5 a.m. to read a book in the pre-dawn silence. Coleman said Billy reads nearly a book a day, that his closet is full of paperback fiction.

But even Coleman acknowledges some of Billy's personal habits are unusual. Billy recently quit his "diet" of two bottles of beer for breakfast (no food, just beer), two bottles of beer for lunch (no food, just beer), and a regular dinner sometimes attended by more beer.

According to Coleman, Billy went from a paunchy 205 pounds to a taim 160 on his diet of brew.

Despite a much-photographed enbrace between brother Jimmy and Billy in Atlanta last week, there were indications that the president was getting annoyed with Billy's remarks, particularly by those taken by some to be anti-Semitic.

"I've told Jimmy, 'If I'm embarrassing you, I'll quit.' He said, 'Go ahead and do what you want to do, I don't care,'" Billy said.

His remarks about the Jews were taken out of context, Billy said. At a Feb. 15 reception given by the Libyan delegation to the United Nations in New York, he told a broadcaster that the Jews "can kiss my -- as far as I'm concerned now."

But Billy told a Post reporter that the broadcaster had repeatedly heckled him while he stood in a reception line, and kept accusing him of being an anti-Semite. The man had made such a nuisance of himself that, several times, he was led away by a security official, only to return again, according to Carter.

Billy crouched beside the seated reporter at the Best Western and spoke almost plaintively of the many Jews he counted among his friends and friends of his family. One, he said, wears a yarmulke and "is orthodox or conservative. I'm not really sure. I don't know a lot about it."