Do you really want to write one?
If you do want to write an autobiography, I suggest that you follow the advice offered by George Orwell in his essay “Benefit of Clergy: Some Notes on Salvador Dali”:
“Autobiography is only to be trusted when it reveals something disgraceful. A man who gives a good account of himself…
They always follow actions
At a holiday gathering last year, my daughter-in-law offered me an old-fashioned doughnut, my favorite kind. I reached for it, then remembered the last one I’d eaten. It had been crispy, sugary, and absolutely delicious, and half an hour later, it had become a rock in my stomach.
I remembered…