Some people have suggested it -that it's just mannerisms he has, it's not something that he thinks about or does on purpose(to fool opponents or something of that sort), and it's not tiredness.
I don't think that's the case, I am not buying it, mainly based on the level his play which most of the time declines with the progression of the games whenever he's played serious minutes. A possible way to see if that's the case is if he does it the beginning of games - if he does, I'd be willing to count it as sub-conscious mannerism he doesn't think about and something that's not dependent on his tiredness. And something else that has to be pointed out, even if that's the case(that it is mannerism), this still doesn't mean he's in great shape, that should be judged on his physical performance in stamina-requiring minutes on the floor.