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.

For example, "[i]n many species of reptile, the oral mucosa may be a bright color that serves to distract the predator". Gaping is part of the shark agonistic display, and is also found in snakes such as the cottonmouth, and in birds ranging from seagulls to puffins to roosters.

Yawning, or gaping, in snakes is usually due in response to discomfort or pain but can also be a sign of respiratory distress as they attempt to take in more air. Twitching can be either normal or abnormal. Sometimes snakes twitch in response to noise, hunger or touch, but it is voluntary and normal.