Is this normal for a 2 year old, or should I get him looked at?

Liala

My son lately has been clinching is fists and tensing every muscle in his body all the way to all the muscles in his face. From what I can tell, it seems to be when he is really excited about something. Sometimes he does it and says he is cold, but there is no way he is cold because he is completely bundled up. From what I remember, he doesn't do it when he is mad or upset.

Is this a normal thing, or should I get him looked at by a doctor?