I have a 50 year history of concussions with my first being very severe and leaving me with permanent dysfunctions. Some of my symptoms could be vestibular. Nobody has ever been able to define a cause. My shaking my head no is not just a casual turning the head, it would be a reactive No, No, No as in when you are trying to impart the seriousness of No to a toddler.

But, you miss my point. Is there something that is causing your tic that also increases your anxiety levels and response ? I think it is far more likely that what ever caused the tic caused the anxiety response. I don't think the movement is causing the response.

I can read an NT post about headaches and get a mild headache sensation. The mind does strange things.

I think your anxiety response is super sensitive to any thought about head movement. I know how the mind can take control. Mine would get stuck looping on meaningless thoughts. The spelling or pronunciation of an odd or complex name or word. A license plate. A stanza from the lyrics of a song. Very small triggers would cause my mind to get stuck on thoughts that had no purpose.

So, if you attribute these anxieties to your mind getting stuck, not the trigger, you will do better. Stress will make these tiny triggers more of a problem. You commented about a stressful period at work. My brother went through a very high stress situation at work (systems analyst at a big insurance company that was transitioning from dumb terminal/mainframe computing to server with thousands of PC based access points.) that radically changed him.

Somewhere, you got exposed to the concept of risk of damage from head impacts/concussions and have used that exposure to define every time your head moves quickly or makes contact. From what you have related, I don't think you have ever suffered a concussion or even a sub-concussive impact. But, your mind has chosen to define those movements and contacts as damaging. Those tics are likely just a response to a stress, whether obvious or not.

My mind did some strange things. I would respond with a verbal Ouch just from the risk or close call of an injury. I could drop something and it missed my feet but I said Ouch. I once dropped a steel plate and broke 3 toes so maybe my brain was remembering. I can also strain to make a lift and say Ouch. Ouch appears to be my response to stress or even potential stress.

I have a few other odd responses. Blowing air through my lips. A moan of pleasure when there was no pleasure stimuli.

I chalk these up to what we call 'Brain farts.' Momentary releases of thought or expression that have no basis in reality or accuracy.

But, you are like the anorexic girl who heard somebody comment about her weight and now is obsessed with every bit of flesh she sees. You might benefit from therapy from somebody who works with anorexia and bulimia. A therapist who works with PTSD may also help as the PTSD responses to triggers are also similar.

So, hopefully, you can find somebody who can help with your underlying response mechanism and help you either change it or learn to ignore it, even laugh at it.