Tom Hanks is squinting out at the Pacific Ocean on an overcast, early summer morning, describing a version of heaven. ''It's the week and a half before you actually start shooting a movie,'' he says in a reverie, peering from behind black Ray-Bans past an apron of Santa Monica sand to the breaking waves. ''You're rehearsing a little bit and you walk onto the set that is gonna be your house for the first time-Oh, look! Oh, look!-and you're trying on the wardrobe. I've always had really good relationships with wardrobe people, which I foster because I have no taste as far as that goes whatsoever, so I'm always at their mercy-Please help me, please come up with some good ideas, what kind of pants do you think I should wear? And your posture sort of changes and you get to slowly get into the work. That's the best.'' Hanks is excited. His head bobs, he leans in, he's a guy describing membership in a really cool club. Then his mouth goes wry. ''Of course, after that it becomes bitter compromise left and right as you slowly wind yourself down to just wanting to be done with it. But, in fact, almost every day of the slow, rolling routine of shooting is spoiling in its simplicity and its completeness. Working in the movies is almost always just as much fun and as glamorous as it is portrayed to be. The work itself is never the way it's portrayed to be, but the actual atmosphere of hanging out and talking to people and watching what goes on, it's a blast. It's a little holy shrine.'' A sun-leathered local pedals by on the beachy bike path, his dog in a front basket with paws draped over the handle bars like a lady receiving a manicure. Tom Hanks sips caffe latte with nonfat milk and looks out at the sea. He is the sweetheart center of the summer feel-good movie Sleepless in Seattle, and at 37, he has known the pleasures and compromises of moviemaking for over a decade. Hanks has been a bona fide movie star since he played an average guy who falls in love with average mermaid Daryl Hannah in the 1984 comedy Splash. And in just five years, he has experienced the full membership rituals of the movie-making club: For his beguiling performance as a 12-year-old boy trapped in a 35-year-old's body in Big in 1988, he received an Oscar nomination, made the cover of Newsweek, and became every man's favorite Everyman actor, every woman's favorite man-boy crush. Just two years later, for his starring role in The Bonfire of the Vanities, one of the defining bombs of recent cinematic history, he was roundly, sternly, critically drubbed. Following which, Hanks took a good long break from the fun and glamorous business of movies, holing up at his Los Angeles- area home and nearby beach house with his wife, actress Rita Wilson (see story on page 18) and their son, Chester, now almost 3. (Hanks' 15-year-old son and 11-year-old daughter from his previous, eight-year marriage live elsewhere in California with their mother, actress Samantha Lewes.) These days, and in the months to come, Hanks knows he is in for another round of scrutiny. Sleepless, summer-light, date-perfect, costarring Meg Ryan and directed by Nora Ephron, opened last month to good reviews, wide-awake ticket sales ($17 million on opening weekend, second only to the omnivorous Jurassic Park) and happy word of mouth from women smitten with the Hanksian character of Sam Baldwin, a grieving widower dad destined to meet cute with a professionally winsome Ryan. He also served with charm and honor on June 25 as first-string guest on the final Late Night With David Letterman. In December, Hanks stars in Jonathan Demme's Philadelphia, playing a brilliant gay lawyer who, stricken with AIDS, loses his job and hires scrappy, homophobic lawyer Denzel Washington to defend him in a discrimination suit. Buzz is already extremely hot on Hanks' performance, for which he lost 30 pounds and shaved his head. ''Yeah,'' he says, glib wit stretched like a protective membrane over momentary discomfort. ''And we shot in Philadelphia and didn't show the Rocky statue, so right away we should win the Humanitas Award.'' On the beach, wary of the sun, Hanks is thin and pasty, with hair rudely cropped -vestiges of his Philadelphia work last winter. On the screen in Sleepless, he is full-bodied, handsome, appealing. But even thin, even sticking to a diet of watery milk-and-egg-white omelets, there is a new dimension to Tom Hanks in evidence, a fullness that has nothing to do with weight of body or curve of smile. The personable guy from Northern California with the benign wise-guy sense of humor who first made his mass-market name on TV in the early 1980s chumming around in drag with Peter Scolari in an all- girl residential hotel in the ABC sitcom Bosom Buddies has gained some gravitas. The boyishness of Big is gone. ''There,'' says Hanks, ''you have it.'' The characters he plays now, he says, are men. He gives a pleased shake of a finger and explains the appeal of Sleeplessness. ''I like that (Sam Baldwin's) motivation was immediately understandable. The guy is enmeshed in grieving, and no one has to work too hard in buying that attractive premise-as opposed to a guy who gets off the airline and picks up the wrong suitcase and it's full of uranium.'' Says director Nora Ephron, who also cowrote the screenplay, ''Tom is a man in a very attractive way. He is never going to spill his guts or confess in some intimate way to anybody. He's not like that.'' In Sleepless, she says, ''Tom is manly in a part that requires him to be tender -and a lot of other things.'' He's one of the few actors around, she continues, ''who can do tender and irritable and angry all at the same time.''