Randomly (meaning maybe once every few months), I will get this incredibly intense shooting sensation up the back of my neck, it's most intense at the base of my skull.
The intensity of the pain knocks me to my feet, and lasts about 10-15 seconds.
This could be muscle spasm, it could be the result of arthritic joints, it could be an irritated nerve, or it could represent spinal instability. Definitely, the latter could be a serious problem, so if it persists I suggest you have it evaluated.