☼.S.
Hi there,
I got these as a kid, too. The only way they would go away is if I was able to go to sleep. My parents took me to the doctor, but he found nothing wrong. Fast forward decades later, I still get them occasionally. What I've discovered is that I not only grind my teeth at night, but I clench my jaw. Both of these actions can create headaches. I even had major gum recession and had to have oral surgery (gum graph). Now I have invested in a bite/mouth guard to wear when I sleep.
Could this be what is going on with your son? Would be worth looking in to. Your dentist can tell you if there is grinding going on just by looking at his teeth. But like I said, it could also be jaw clenching, which I don't believe would show up on his teeth. Good luck.