My earliest memory is from when I was 3. I went with my mom to go pick up my older brother form kindergarten. This was also right by where I would be going for preschool starting that fall. There was a shared playground between both buildings. What made this memorable was all of the blocks in his classroom. We had a lot at home, but there were many blocks on the shelves on the wall. The other thing that made it memorable was when I went to try out the slide, I discovered that metal objects out in the sun (especially in Arizona) get really hot. My identity is the same as it was then, but my personality has changed I believe.
Like you I remember one random event in my early life. I remember a specific detail about the memory that helps me visualize it. For you it was the blocks in the classroom, but for me it was the vast backyard that looked perfect in the great weather.