Yes, snakes will "yawn" for a variety of reasons. Quite often they will yawn after eating in order to realign their jaw. They also seem to yawn occasionally for unknown reasons... perhaps for the same reason we yawn.

However, sometimes they will yawn frequently because they have a respiratory infection and they are trying to get more air into their lung. If you suspect this is the case, I would recommend that you get your snake to a vet ASAP as this condition can be fatal. You can also look for other signs of a URI such as drooling, keeping their neck stretched up, and bubbles coming out of their mouth.