The simple answer is that if this head jerking causes symptoms, the symptoms are what matters. Causation could be trauma to head, neck or anxiety. If the jerking is violent, attention needs to be paid to try to stop the jerking.

It is hard to believe that a single jerk could be damaging. Multiple violent jerks could combine to be considered traumatic.

My opinion is that you aggravated your neck injury. There is a huge overlap between concussion symptoms and upper neck injury symptoms.

I doubt even a specialist could tell you accurately what caused your symptoms.

How far do you jerk your head during these events ? Front to back or side to side ?