J.M.
He's at about the age where kids stop wanting/needing naps. When they go through that (or at least when MY boys went through it) it's like their mind wants to get up, but their body is used to sleeping during that time, so it fights waking up. They'll behave as though they're tired & cranky when they would usually be sleeping until their body adjusts. That was my experience, anyway. Good luck...I'm sure he'll get over whatever he's going through soon!