:Psammophis (your snake) have a very interesting behavior that I believe you are describing. They secrete an oily substance from their lower jaw which they rub all over themselves. It is thought to protect against the sun and dessication or perhaps aid in locomotion through sandy habitat. I believe this is what your snake is doing. Two things that you might consider.. Mites can cause irritation and behavour similar to what you are discribing, also, this time of year many snakes naturally go off feed until spring. I would suggest that if no mites are found, and your snake otherwise appear healthly, Over-winter him by reducing the temperature and lighting and try feeding him again in the spring.I he has mites you will see little white or black specks about the eyes.