Photo: Santiago Felipe/Getty

William Shatner visits SiriusXM Studios on September 6, 2018 in New York City

William Shatneris reflecting on his own mortality.

The 91-year-old actor, known for playingCaptain James T. KirkonStar Trek, admitted thathis ageplayed a factor in deciding to makeYou Can Call Me Bill, a documentary about his life.

“I’ve turned down a lot of offers to do documentaries before. ButI don’t have long to live,” he toldVariety. “Whether I keel over as I’m speaking to you or 10 years from now, my time is limited, so that’s very much a factor.”

“I’ve got grandchildren,” he continued. “This documentary is a way of reaching out after I die.”

Shatner shared that he doesn’t wanthis knowledgeto go to waste after his death.

“The sad thing is that the older a person gets, the wiser they become and then they die with all that knowledge. And it’s gone,” he explained. “It’s not like I’m going to take my ideas or my clothing with me.”

Emma McIntyre/Getty

William Shatner

He added: “Today, there’s a person going through some of my clothes in order to donate or sell them, because what am I going to do with all these suits that I’ve got? What am I going to do with all these thoughts? What am I going to do with 90 years of observations? The moths of extinction will eat my brain as they will my clothing and it will all disappear.”

Shatner also recalled discussing the idea of a legacy at a Red Cross fundraiser at Mar-A-Lago, which caused him to miss hisStar TrekcostarLeonard Nimoy’s funeralin 2015.

“When Leonard Nimoy died a few years ago, his funeral was on a Sunday. His death was very sudden, and I had obligated myself to go to Mar-a-Lago for a Red Cross fundraiser,” he said. “I was one of the celebrities raising money. That event was on Saturday night.”

“I chose to keep my promise and go to Mar-a-Lago instead of the funeral, and I said to the audience, ‘People ask about a legacy. There’s no legacy. Statues are torn down. Graveyards are ransacked. Headstones are knocked over. No one remembers anyone. Who remembers Danny Kaye or Cary Grant? They were great stars. But they’re gone and no one cares,'” he shared. “But what does live on are good deeds. If you do a good deed, it reverberates to the end of time. It’s the butterfly effect thing. That’s why I have done this film.”

William Shatner in Star Trek.CBS Photo Archive/Getty

William Shatner in Star Trek

“I’ve made all these films that are popular, so I’m sure they’ll pop up every so often. But I don’t need validation from a film I made in 1982,” he explained. “I get pleasure in talking to you right now.”

Never miss a story — sign up forPEOPLE’s free daily newsletterto stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.

You Can Call Me Billisset to premiere at SWSXon Thursday, March 16.

source: people.com