Ok, I don't remember objectively but, from what others told me:
I started talking a bit late (not so late it would be abnormal though) and it were full sentences
I was obsessed with colors
There were songs and books I listened to, or wanted to be read to me over and over and over again
Certain objects fascinated me (I liked going to museums, and once there was abstract sculptures exhibit which was not large but we spent two hours there, because I was just walking around fascinated with those sculptures)
I was very difficult to put to sleep
I was extremely afraid of people with long/er black hair for some reason
Sometimes, I was unresponsive and I kept talking on and on about certain things (I have it taped)
And, for the life of me, parents were unable to teach me certain things (shoelaces) I figured them later by my own while, on the other hand, I was very, very good at remembering things.
None of things seemed a big problem at that time, the problems got more visible as I grew older and had to interact. In my country, compulsory education begins at the age of 7, before that there is kindergarten which is optional. I was there for a year, it wasn't working very good, so mom pulled me out and after that, I was home-schooled (until 1st grade) and it went great.