By what we identify as yawning, they are stretching and realigning their jaws in order to either prepare to eat, or to readjust themselves after eating. Your snake may yawn once or even multiple times to reposition their jaw comfortably, which is completely normal.

Yawning is involuntarily opening the mouth and taking a long, deep breath of air. This is most often done when you are tired or sleepy. Excessive yawning that happens more often than expected, even if drowsiness or weariness is present is considered excessive yawning.