Why do I have to keep my legs moving after working out?

This is something that has always happened since I was a kid. I always thought it was simply nervous energy. I had to move my legs to rock my bed till I fell asleep. When I would sit for a while, my legs would start to bounce. I just didn’t like sitting still. It has been years and after my workouts now, I am back to where I started. As I’m sitting here typing this, my legs are bouncing. I have been that way for two days. Funny thing is my legs can be tired and yet it feels nice to keep them going. Luckily it doesn’t happen in bed before I sleep.

By the way, it is not the medical restless leg syndrome. It’s just that I can be sitting not thinking at all, and without any thought my legs start to bounce or my foot start to rock back and forth. I can make it stop but when my mind drifts on to something else, it starts back up again.