That’s the issue, isn’t it?
Publishers buy books that will make them money. And generally, even if your life actually was really interesting AND you are able to create a compelling narrative about it, it’s very hard to make anyone believe they will be entertained if they’ve never heard of you.
Writing down your memoirs, especially if you’ve participated in a niche career/pastime or been part of a notable historical event, is highly valuable and advised! And maybe you can self-publish through a print-on-demand service, gift copies to your inner circle and/or distribute copies at shops or venues related to your life’s subject matter, or buy some ads promoting it. You aren’t going to get into mainstream publishing with an autobiography sold as nonfiction unless it’s already made some kind of wave some other way. This fact doesn’t mean your work and life aren’t valuable. It means there’s an issue with the sales angle that’s almost impossible to overcome.
Other options if you’ve had an Interesting Life and really want to share your stories with a wider audience:
Recap some of them as short stories and sell them to magazines.
Recap some of them as skits and try to sell them to anthologies.
Rewrite it as fiction, if you think you can turn it into something reasonably plot-driven. (This is difficult to do right, but it’s been done.)
Get known for something else (or reach out to contacts in a place you’re known) and ask for opportunities to talk about or share the book. This can work really well if, for instance, you’re a comedian and your stories get people laughing, and they’d enjoy the idea of picking up your book after. Or you start a blog that provides content no one else is providing and see what people have to say for a while before you start promoting a book with the collected stories.
There are a lot of ways to do it, but the bottom line is that if you’re Joe Nobody whose life mattered to your co-workers, friends, and family but you have no name recognition outside your family reunion and your church, mainstream publishing attempts are almost definitely going to result in eternal limbo.