Richard Nixon is back on the "fastest track in the world," as he calls New York. He's out walking the early-morning streets. Signing autographs at Yankee Stadium. On television. At "21." At Luchow's. In Central Park. On 57th Street. He's back with a new house, a new office, a new book, new enemies (or at least a new name for the old ones). He's ready to talk. Grant access. Open the door. Be heard from again. Take a walk with the Daily News. Go to a few private dinners.

In February, Nixon moved into the narrow 12-room, red brick and gray stone houst at 142 E. 65th St., where Judge Learned Hand lived for 50 years. He has six fireplaces (which he made sure worked), central air conditioning, a nursery for his grandchildren and a well-tended garden with a one-bird birdhouse.

Like many New Yorkers, he had trouble finding the right place to live; he had to compromise and pay a lot ($750,000), and do some construction of his own. Unlike other New Yorkers, he lives with armed men in his basement and entrance hall.

I saw him in his study, where the few presidential relics are oddly placed -- the presidential seal embroidered by Julie behind the door, and only six elephants on top of one of the bookcases that contain no Watergate books. He points out a third-century Buddha with Greek features given him by the king of Afghanistan, who told Nixon it was in Kabul that Alexander the Great had said, "I have no further worlds to conquer."

Nixon seems calm, in harmony with the very Oriental feeling of his house -- the ricepaper walls and Chinese decorations. He seems lonely. Pardoned, but, by many, unforgiven.

Early-morning walks are now his only exercise, though he'd like to find a neighborhood bowling alley. "I've never been much of an exercise buff. On occasion, golf, the ocean, pools. Here I walk every day early . . . a mile and a half to two miles. Ten of the short blocks and 15 long blocks -- the Secret Service tells me each is one-tenth of a mile. They measured . . . The Secret Service goes along. One person, and he walks somewhat away. The joggers keep to themselves, but they look up with a start. I don't see the dog-walkers till 6:30. I see delivery people and cabdrivers, the restaurants that are open all night. Sometimes I'm invited in, but I don't go."

Before his walk, he puts on a business suit, has grapefruit juice and makes himself coffee. Manolo Sanchez, his White House valet, has retired to Spain, and the Nixons have hired a Chinese couple.

"I walk even in the rain. I own a raincoat. I don't take an umbrella. . . . Today, I saw my doctor, Dr. Klein, at New York Hospital. I'm on Cumanden -- it's a blood thinner for phlebitis, to prevent the blood from clotting. I asked him about jogging. Some of them look like they're going to die. He said it's not good unless you were always an athlete, but to take it up at 50 or 60 is dangerous. I don't think [I'll do it]."

After his walk, Nixon reads the papers: The New York Times, the Wall Street Journal and the Daily News. He also has a young man who reads 30 to 40 magazines for him and prepares a weekend reading list.

At 7 each morning the Secret Service drives Nixon to his new 15-room office at 26 Federal Plaza on Foley Square. Many times he gives Ed Cox, his son-in-law, a ride down to Cox's law firm. Nixon's office is on the 13th floor behind an unmarked door, totally anonymous until the door is opened to a view of orange walls covered with Ollie Atkins pictures of Nixons. To the right of the door there's a 2-foot photo Rolodex with homey family snaps of the kind of family that collects Boehm birds.

In his private office he has seven enormous ribbon-hung flags -- five genuinely imposing service flags given to former presidents, plus the two flanking his desk: an American flag and one with the presidential seal. On his table is "The Poems of Mao Tse-tung."

He does not go out for lunch, but has a tin of salmon with a little mayonnaise and Rykrisp. He always works in his suit jacket, never in shirtsleeves, because he has a tendency to catch cold.

He goes to the office every day, preferring Saturdays and Sundays when there is nobody there, nobody in the building. Though six people work for him, including his former speechwriter, Ray Price, they are still hiring and Nixon says he is understaffed. His office budget if $239,800.

But what does he do from 7 until 6 every day? One friend describes it as "the ongoing business of being a former president." He signs his letters, autographs his books (in just one recent week he finished signing 19,000) and he "sees people," says an aide. On most nights Nixon is home for dinner at 6 and in bed by 9 or 10.

He sees Tricia and Ed Cox three or four times a week. "She's only five shorts and three longs away," at 10 East 70th. His year-old grandson Christopher is "not on the talking side but very mechanical -- he can put anything together. He has a cash register. It takes three motions to run it. I can't do it," he says.

Every two or three weeks the Nixons drive down to see Julie and David Eisenhower and their daughter Jennie in Berwyn, Pa. David is working on the "definitive" Eisenhower biography, and Julie has temporarily put aside her book on Pat because she is expecting another baby in October.

"When Nixon moved to New York in 1962," Henry Kissinger writes in his "White House Years," "he was shunned by the people whose respect he might have expected as a former vice president of the United States who had come within an eyelash of election as president. He was never invited by what he considered the 'best' families. This rankled and compounded his already strong tendency to see himself beset by enemies."

"I think after this book I'll be a little closer to people and the whole public arena," Nixon says. "There are friends, the people who wanted to see us in California," but for the first three and a half years he was working on his memoirs, and the next year and a half on his new book, "The Real War," and San Clemente was hard to get at. "Here they fly up from Washington and in from California," and he says his life is more active and involved than in the San Clemente period.

A part of Nixon is genuinely antisocial. Though he says he needs mental stimulation, he sees those who do not challenge him and will not mention Watergate. Thus, he sees sympathizers, groups of young people, an eighth-grader from Harlem.

He tries to avoid crowds. The Nixons can't really go to the theater because of what he calls "the recognition factor" or "the fact of being a celebrity." He's been to some large restaurants -- "You pick up a big tab," he says. It's even hard to go to church. He hasn't yet been because of "getting moved in" and the crowds, though eventually he will return to Norman Vincent Peale's Marble Collegiate. He went to see his old chum Ginger Rogers at the Music Hall and to a game at Yankee Stadium.

Nixon is in a weird status quandary of being ex-president of the United States and yet . . . Nixon. The old us-them bunker mentality is in evidence and now reinforced by the course of his life and the world as he sees it. On a social and political level, it's what he calls the "trendies," the "sophisticates," the "Beautiful People" and the "art crowd," as on a global level it's the Soviets versus the United States.

I asked Nixon what he would choose as a metaphor for New York.

"Well, I had a description many years ago from a fellow [of] the difference between Paris and Rome. Paris is like a beautiful jewel, beautiful but cold; Rome is like a warm fur coat. Manhattan can be either one . . . A combination of a warm fur coat, if you are in the right circles or can afford it, or it can be ugly and cold at the same time. The thing about Manhattan, I say, is this: In a way (one) may love or hate, like or dislike it, but it's never dull . . . . People who want a quiet life, unchallenged, should not (live here). It's the fastest track in the world."

I asked Nixon if he is happy.

"I take life as it is," he said. "The main thing is to have a project or a challenge. Some people think the ultimate in happiness is to have nothing to do. In my bracket, they retire and die, or they go to Palm Beach, swim and golf and go out. I don't like fishing and I never hunted." And he has given away his golf clubs.

Nixon is 67 years old. Only he knows what his definition of vindication is. In the past he has come here to recharge himself, and always to begin things, never to end them.