I don't like making new threads on topics that have already been discussed, but either I'm bad at searching the forums or I'm just bad at searching the forums. Lol
Anyway, I've noticed at times that Izzy will kind of, like... Puff his body and beard. He feels really hard and almost flat when he does this. It seems he does it for no reason, and (to me) doesn't look aggressive. But I could be wrong.
I also don't think it's due to shedding since he does it at random times (again- I could be wrong), even when he isn't shedding. He does it for about 30 seconds to a minute at most. Usually I'll pet him and he slowly deflates and acts fine. I did try to get a picture, but he saw me and started shrinking again.
Sometimes it's to loosen a shed as you say, sometimes it's mood related. They often pancake to increase surface area when they bask too. It's tough to say what the exact cause is in this case but the behavior is pretty normal and if he's reacting well to you and not doing it for very long I wouldn't worry about it.