Do kids personalities change over time? My son is suddenly shy at age 3?

I was shy for a long time and timid, and then when i turned 11 it seemed that a huge light when on in my body and suddenly i was energetic and excited and i would dance in public and LOL whenever. So i was a little sourburst of energy !!! When i was 19, that's what attracted my hubby mostly and my hubby evens me out now so yes and now that i have a baby i definitively have to keep my high energy up. So your son will sprout into a social butterfly before you know it, most kids do !