Oh yeah, yawning. Mine does it ALL the time. Before sheds, during them, after them, between them, when I'm holding her, any time. When I begin handling her, she is very shy and timid and doesn't move much, until she yawns at least once, sometimes more, about 5 – 10 minutes later. Then she perks up, sort of like a stretch I guess. I usually handle her for about an hour, and she typically yawns 2 or 3 times. It just seems “normal” for her.

I think it's kind of cute, actually. My boa certainly doesn't do anything like that, though he does do this silly looking sort of “lip readjustment” thing.