David Hasselhoff is trying to be serious - not easy when you are wearing nothing but a shorty bathrobe without buttons. During a break from the COSMO shoot, he is reminiscing about the thrilling moment last New Year's Eve when he sang at the Berlin Wall. Above it, actually. Perched atop a huge construction crane - "Five stories high, with fireworks exploding all around me!" - he belted out his top-of-the-chart single, Looking for Freedom. And the throngs of revelers joined in!

"I went there to say thank you to the German people for having embraced me as a singer," David earnestly explains. "It was a very emotional night."

A singer? Wait a minute. This is David Hasselhoff, the hunky hero on NBC's Baywatch, right? And wasn't he Michael Knight on Knight Rider for four years.

Right again. But this thirty-seven-year-old, six-foot-four actor, with turquoise eyes and a finely tuned athletic build, is also a singing sensation - in Europe. David actually started out in musicals - he played in Peter Pan a kid in Atlanta - and has been chasing a music career ever since.

Though U.S. deejays aren't hot to play songs by "that guy who talked to the car," David says, Knight Rider's immense popularity abroad (incredible, it's still running in sixty-two countries) has helped his two albums (Lovin' Feelings and Looking for Freedom, both sung in English) go platinum and gold in several countries. His live Knight Rockers musical show plays to sellout crowds.

When not in front of a TV camera or behind a mike, he devotes much of his time to another passionate interest: being a buddy to seriously ill children. He visits them, entertains them in his home, even makes get-well videos. "My involvement is very intense," he says. "I have seven scrapbooks filled with letters and photos, and some heartbreaking stories..."

David sounds so unself-consciously sincere, you have to believe him when insists that in Baywatch, it's the sensitive scenes with his character's young son that he likes the best - not the macho ones that show off his bare, bronzed chest.

David's other intense involvement is with actress Pamela Bach, twenty-seven, whom he met at a restaurant opening. He threw away her phone number that first time - but when they ran into each other again a short while later, the attraction was instant, and mutual. Married this past December, the couple live in Los Angeles house that has, well, everything: a superbly equipped gym, steam room, basketball court, pool - all of which they share with seven dogs, two cats, and three noisy parrots (one barks, another makes doorbell sounds!). A new resident, their first baby is expected in June.

The prospect of becoming a father only spurs David on to test himself against greater challenges. Coming up: a major international singing tour, a two-hour Knight Rider special that he is producing in the fall, and - if he finds the right property and his luck holds - maybe even a starring role in a musical comedy.

"Suddenly, I'm attracting terrific projects I never expected," he says. "Everything's happening - including COSMOS's centerfold. And you know the best part about that? he demands with a dangerous twinkle. "I get to keep the wardrobe!"