What does a guy do when he’s still in his 30s and has already achieved everything he ever dreamed about?

The actor Zach Braff was turning over that question the other day at a diner in Midtown Manhattan. He was discussing the problems facing Harry, his character in “Trust,” a new play by Paul Weitz that is in previews at Second Stage Theater (Aug. 12-Sept. 5), but Braff might as easily have been talking about himself. Last year he wrapped up filming a ninth season as John Dorian, or J.D., the lead character in the television show “Scrubs,” a role that brought him wealth and fame, as well as the chance to write and direct his own movie, “Garden State,” a critically praised romantic comedy. After so much success, where do you go?

“I’ve had this wonderful, blessed, lucky last 10 years, but you kind of go, ‘OK, I’m 35, what else is my life going to be about?’” Braff said.

That question is paralyzing for the fictional Harry, who has sold his Internet company for $100 million, but is stuck in an unhappy marriage and suffering from ennui. The play starts off with his visit to an S-and-M parlor to try to rouse himself, and having an encounter that offers a potential new path.

And Braff? Is he on the verge of an existential crisis, too?

It wouldn’t seem so. Sitting in the diner wearing a fedora and shorts, along with two days’ worth of beard, he was the picture of confidence as he discussed how “Scrubs” meant that he could do, well, pretty much whatever he wanted for the rest of his life.

“I’m just enjoying this play so much,” he said, adding that he e-mailed Bill Lawrence, the creator of “Scrubs,” to say, “‘I just want to thank you one more time for giving me my dream life.’”

After “Scrubs,” he said: “I put it out to my folks that I want to do challenging things. I don’t care if they pay a dollar, I don’t care if I have to help set the lights.”

The film he just shot, “The High Cost of Living,” which was made with French-Canadian actors and is partly in French, is a perfect example of the kind of work he wants to do, he said. “I like dark little art movies,” he explained. “It’s something that, if I saw it at a festival, I would go, ‘Wow,’ and tell my friends they have to see it.”

In person Braff is ingratiating, if not endearingly hapless, like J.D. in “Scrubs,” or soulfully morose, like Andrew Largeman, his character in “Garden State.” He ventured a few jokes.

Doing a play was at the top of his wish list after “Scrubs” ended, he said. He grew up watching his father do community theater and spent two summers at Stagedoor Manor, the theater camp in the Catskills. From the camp he got an agent, who sent him on auditions throughout high school. He did a pilot when he was 14, and, when he was 18, played Woody Allen and Diane Keaton’s son in “Manhattan Murder Mystery.”

After going to college at Northwestern, where he studied film, he performed in two Shakespeare plays — small roles in “Macbeth” at the Public Theater, directed by George C. Wolfe, and Romeo at a regional theater in Connecticut — before starting “Scrubs” in 2001. (He made a brief return to theater in 2002, when he played Sebastian, alongside Julia Stiles as Viola, in “Twelfth Night” in Shakespeare in the Park.)

“Trust” was appealing, Braff said, because it was “sexy and dark and risque, and first and foremost funny.”

Weitz has had two other plays produced at Second Stage, “Privilege” and “Show People,” but he is better known for his movies, which include “American Pie” and “About a Boy” (both of which he directed with his brother, Chris), and “In Good Company.” In a phone interview, Weitz said that Harry’s problems were inspired by his own experience of finding that success “threw things out of whack in my other relationships.”

Braff continues to push into new territory, though. He is writing another screenplay, and he has also written a play, titled “All New People,” a dark comedy with four characters set during winter in a beach house on Long Beach Island, N.J.

He would not reveal the plot, but said that there were “some people that are very interested in it, so hopefully you’ll get to see it.”

As for future stage roles, he said he would love to do Broadway “when the right thing comes up.” He described himself as a fan of musicals and said he was working on his “Trust” co-star, Sutton Foster, to sing a duet with him at the theater one day. “She was Eponine once on Broadway, so I want to sing the Eponine death scene,” he said. While Braff knows that television made him famous, he considers himself a product of the theater, thanks to that job in “Macbeth” at the Public. “I feel like this is where I started,” he said. “I was lucky enough to go work in TV and film, but I hope I’ll be allowed to be one of the people that goes back and forth.”