What you are having is a tic which is a sudden, repetitive, nonrythmic, motor movement or vocalization involving discrete muscle
groups. These must be distinguished from other movement disorders like chorea, dystonia and myclonus. Simple motor tics are typically sudden, brief, meaningless movements that usually involve only one group of muscles like eye blinking, head jerking or shoulder shrugging. also seen are neck stretching, mouth movements, facial grimacing etc.