No such thing as a silly question
Your temps are great. Sanichips are a little dry. For balls I really like 50/50 Cyprus mulch/coconut fiber. Its really easy to maintain the right humidity that way. Once I Switched to it my ball had her first complete shed ever.
Does he do this when he gets in his water bowl also? Or just when you go to soak him?
If its just when you soak him, he be uncomfortable with being put in water. They usually get used to it.
He could also be constipated. I've seen constipated snakes do the same in water. It's easier to pass it seems. If you gently run your fingers down the abdomen to the vent you may feel if he is. If he is he'll need a warm soak.