At first we thought DS was choking as he would stop breathing and turn red while he was eating. Nope, no food stuck in there. Then he did the same thing a few times while playing. I'm guessing this is just a new discovery so he wants to keep trying it out.
My LO has never done it however my brother did. My mom said when he got mad, he would hold his breath until he passed out a couple of times. It is his way of controlling his enviornment to an extent. The worst case senario is like my brother that he will pass out and start breathing again. My bro is now 30 and doesn't appear to have suffered any ill effects from him holding his breath epiodes.
Hampton used to do that. Like you said, I think it was something fun he discovered he could do, and thought it was fun. I wouldn't be too concerned. If he holds it too long, I might interfere and make sure he lets it out!
Re: Holding his breath