Mine does that (yawn) from time to time, maybe she is bored in her tank.
She ate a small rat about a half hour ago then she yawned a couple of times just after the tail went down her throat.
Harry
from Atlanta
0.1 normal 3,200 grams 5 feet long
100 gallon tank with 4 UTH
3 are thermostat controlled, the 4th one is constantly powered located directly under the water dish.
17" x 13" clear glass rectangular baking dish (5 quart) for her to soak in