Theta,

I was able to read your post. I have an event from time to time that may or may not be similar to yours. I will have a jolt to my head. It appears to be similar to when I start to fall asleep while sitting up. The relaxation of my neck muscles is met with a quick reaction to hold my head up. Does this make sense?

As soon as my head starts to drop forward, it reacts with an almost whiplash to 'right' my head position. Sometimes, the sudden movement results in the feeling of a concussion.

This tends to be more frequent when I am trying to hold my head still with stiff neck muscles. Could it be the muscle tension is causing a spasm of those same muscles?