Have your son go speak to the team doctor, may sound silly to do so, but if it is interrupting his sleep he needs to let someone know. Sooner or later it might take it's toll. It basically sounds like anxiety and they will help him with it. Sounds like me before I have to catch a plane, I can't sleep all night, afraid I will oversleep, yet I very rarely use an alarm clock.
My son has been to the team doctor for a variety of reasons (he rarely went when he was growing up). I think, to him (he would not admit it), team doctor is as close to a mom he's gonna get at school.
Don't laugh, first day of class as freshman the coach called all of the kids (4 of them) to make sure they were up, too funny.