My DS is like that too. It definitely depends on the amount of sleep he gets and the problem is usually nap time. For us, getting some food into his quickly seems to help. Something like fruit, yogurt, with some easily digestable sugar.
I didn't intend to go the TV route and we would let him watch a 5 minute tivoed show, but we stopped doing it when he'd be more and more demanding/irritable when the show was over and it was time t move on.
She'd be his wife and make him her husband 5/03Ds1 12/22/09...Ds2 8/31/12