My ds just turned 2 and is either asleep, drinking his milk on the sofa or else climbing the sofa and any other peice of furniture he can manage to scale up!
He is never still and never wants to just sit, even at meal times grrrr. He was the same even when he was tiny, he just gets bored easy I think!
He sleeps from 7pm - 7am and naps for around 1.5- 2 hours a day. I think kids like this tend to sleep well cos they are exhausted from all the activity.
I wouldn't worry. I don't know any 2 yr olds who just sit still. The more active they are, the more they are exploring and the more they are learning!