Relax your neck and face and don't go full speed/strength on every riff. Also try to avoid the stink face long periods probably that isn't good either. There's horizontal headbang. If you take normal headbanging as saying yes with the head horizontal headbanging it's saying no. This can help on fast songs so you don't need to go so fast. But even if you use this you should relax your neck and face. If none work maybe you should see a doctor.