First off beautiful snake. Is he a bamboo? He may be moving around a little and your just not there to see it. I have a few that spend almost all their time curled up under their paper towel with just their heads poking out and are hardly ever active. On the other hand I have several that are very active. He looks really healthy, I wouldn't worry about him. Also like the above post mentioned look out for when he goes blue if you miss him going blue look for the pinkish red belly thats when you know they're going into shed.