I have this happen to me too. I've found it usually occurs if I yawn with my head turned to the left or sometimes when swollowing, otherwise sometimes randomly. It comes as a severe pain in my neck that usually radiates up to just under my jawbone. I actually believed it was something with my jaw for the longest time until I figured out that something in my neck had popped out of place. I realized I could push with two fingers on this ring-type-thing to pop it back into place and the pain stops immediately. I actually can't talk or swallow when the pain is there because it's so bad. When I do pop it back in, there is an audible 'pop' that happens. My significant other can hear it when I pop it back into place.

The only thing I can think of this stemming from is a car crash where I was T-Boned. The doctor checked me out and said I was fine with a minor case of whiplash, but I wonder if that jerk/bend of my neck could have caused it?