WHETHER BY horsepower or quarter horse, William Shatner, like a force of nature, continues to go where relatively few octogenarian performers have gone before.

Just glance, for example, at random log-date entries on his appointment schedule. Next month, he’ll embark on a Chicago-to-Los Angeles road trip, piloting a three-wheeled motorcycle dragster built specifically for him by American Wrench. Later this summer he’ll head to Asia for a reality show; then in October, he’ll take his one-man show to Australia.

Why does the Emmy- and Golden Globe-winning actor do it, exactly, crossing borders and continents to entertain and seek thrills, a half-century after Gene Roddenberry’s “Star Trek” first put Shatner in the driver’s seat? “I don’t know,” he says by phone, with a bit of the dramatic pause that’s his signature. “Maybe because it’s out there.”

He mulls the question for another moment. “These physical feats are out there — why would I say no? And just go walk around the house?” (Which, by the way, is being renovated for yet another Shatner project: a DIY Network show. Even at home, he’s on the go.)

“I’m living in sort of a dream until I can no longer do it,” Shatner tells The Post’s Comic Riffs.

This weekend, that dream includes appearing at Awesome Con, a three-day festival that will draw thousands of pop-culture geeks to the Walter E. Washington Convention Center. The man known to so many as Capt. James T. Kirk, T.J. Hooker and Denny Crane (“The Practice” and “Boston Legal”) will appear Friday and Saturday, and is eager to talk about his favorite new comics enterprise, “Man O’ War.”

“I think,” Shatner says dramatically, “that I’ve invented something new. It’s a comic book — or illustrated novel, as they call them now — over which the camera roams: the panel, the dialogue. But we have sound effects, and music.” That sounds similar to a motion comic — an existing format — but he insists with Kirk-like passion, always happy to engage: “But I think I’ve gone another step.”

A step Shatner says he won’t be taking? One toward his former “Star Trek” castmate George Takei, the social-media star and LGBT icon who will appear Saturday and Sunday at Awesome Con. The two have traded long-distance barbs for years.

“George is rather a strange fellow,” Shatner says, noting that the two don’t engage socially. “I didn’t know him [on the ’60s show] — I don’t know him. He doesn’t seem to recognize that 50 years ago, he came in and out [of the show] on occasion. He had a small part. I would see him very occasionally.

“I don’t know him — what’s his beef?”

By contrast, Shatner expresses much warmth for Leonard Nimoy, who died at 83 earlier this year. “I lost a beautiful friend and a man who made me laugh,” Shatner says of the actor who played Spock. “I loved being on stage with him – and his laughing himself silly.

“But it’s a note of warning to me about age, and that it’s catching up to all of us,” adds Shatner, who turned 84 in March.

And so Shatner will attend more comic conventions and more film events. He was on hand this month at the New York International Film Festival to support his new documentary, “Chaos on the Bridge.” He will win more blue ribbons riding his quarter horses, and will politically support a Columbia River pipeline to bring more water to California.

And mostly, when appearing in public, he will commit himself to doing one essential thing with an audience: Engage.

“When I appear onstage, I try to make it a happening,” says the performer, six decades in. “It’s an exercise in improvisation. I don’t pretend to have any great wisdom I’ve retained. It’s a give-and-take with the audience.

“And I am exhilarated.”