Starting an autobiography with action will help the writer generate the outline to follow. Some people choose their defining moment as an event that happened in early childhood that shaped their career or personal goals. That one moment spurred everything that was to come in the life to follow. Choosing a defining moment from your life gives clarity to the style of autobiography you wish to pursue. From that moment, you'll be able to organically shape chapter points to your outline based on (and related to) that shocking beginning.
In the case of the famous "Angela's Ashes" by Frank McCourt, he begins his autobiography writing about himself as a scrappy 4-year-old poor Irish kid whose sister has just died. Tragedy, a desire to stay alive and honest writing define that autobiography.
Pick your defining moment and then write from the guts, without editing when you get scared. Go with it. That'll be your best stuff.
Don't have a defining moment? The great thing about an autobiography is you already know the story because you've lived it. You can just follow the stream of your life, and the chapters will already be neatly laid out for you.
You may want to start with your birth, or introduce your parents, give a little bit of detail about their ancestry and lifestyles. Where do you want your autobiography to start? Where do you feel your life started--before you were born when your parents first met? In another country where your great-grandparents met by chance while fleeing their homeland? Everyone's beginnings have pieces of fairy tales in them. You'll want to write down the facts, starting as early in your "life" as you wish, and moving forward to your present life. This will become your natural outline.
As you write down the different sections of your life, you may find a section that leaps off the page as the most dynamic to you. You might find that as you start writing, your autobiography becomes strongest around this section. Write it all anyway, but be aware that the finished product might center around this meaty section while the rest is just decoration.
In the end, what has life meant to you? What (or who) holds meaning, scope, depth for you? This will be the tone of the autobiography, and will help you shape your outline. Writing about your own life requires a passion for the things you care most about--enough passion (or horror, in some cases) to fill a whole book.
You might want to start at the end, where you are now, and work backward in your outline, the way you'd tell the story to your grandchildren. The perspective that is gained with hindsight can add a dimension to the outline and eventual finished piece.
Pick your tone, say what you can say as honestly and vividly as you can let it come through you. As you are outlining, check yourself for honesty. When you feel it's become tedious, think: "What's the thing I'm not saying? What am I/was I scared of the most at this point in my life?" The truth will bring humor, passion and universal appeal to your finished work.