William Shatner Looks for Ways of 'Reaching Out After I Die' as 91-Year-Old Actor Admits 'My Time Is Limited'

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William Shatner is reflecting on his own mortality.

The 91-year-old actor, known for playing Captain James T. Kirk on Star Trek, admitted that his age played a factor in deciding to make You Can Call Me Bill, a documentary about his life.

"I've turned down a lot of offers to do documentaries before. But I don't have long to live," he told Variety. "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."

RELATED: William Shatner's Fascinating Life, from Star Trek Icon to Real-Life Astronaut

Shatner shared that he doesn't want his knowledge to 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."

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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."

RELATED: William Shatner Reveals He Has 'Never Watched' an Episode of Star Trek: 'It's All Painful' 

Shatner also recalled discussing the idea of a legacy at a Red Cross fundraiser at Mar-A-Lago, which caused him to miss his Star Trek costar Leonard Nimoy's funeral in 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."

CBS Photo Archive/Getty William Shatner in Star Trek

RELATED: William Shatner Thanks Fans for Well Wishes, Calls Reaction to His 90th Birthday 'Overwhelming'

When asked if he is comforted by the fact his films will outlast him, Shatner replied, "They'll be good for another 10 years, maybe five."

"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."

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You Can Call Me Bill is set to premiere at SWSX on Thursday, March 16.