You can write an autobiography whenever you feel ready to do it and you don’t have to put it all in one book. Maya Angelou wrote about her life in six books. Vladimir Nabokov wrote about his life and each chapter had a theme: escaping Russia, Butterflies, writing, and several others.
I like memoirs and autobiographies because I find other people’s lives fascinating. They have had experiences I may never have but for whatever time it takes to finish the book, I’m right there beside them. That’s how you should think about your life story. What things have you seen, done, laughed at, cried over, celebrated, and mourned? It’s the human experience, the things that make us see that we’re more alike than we are different. That’s how you engage your readers.