What is wrong w/ my friend?

Ok so my friends and I all got together the other day and we were sitting in the living room chatting, and one of my friends kept doing this thing where he would start like huffing and puffing, or like deep breathing or something, you know when you get excited or overwhelmed or something and you start breathing deeply, yah so he was doing that and he would hold his hands up and like squeeze his hands together and stuff then, after like a minute or so, he'd stop. My friends and I just acted like we didn't notice so that he wouldn't feel all weird. What on earth is making him do that? It almost seems like he's nervous or excited or something, but he's not, it's just this thing he always does. Is it just like a bad habit, like how some people twitch their nose, some jerk their head, and some crack their knuckles??