My 24 year old daughter has uncontrollable head shakes. She had two major head trauma's a few years ago could that be the cause

Yes. Trauma brain injury frequently has long term sequlea. Talk to your doctor or consult a neurologist to see if there is anything that can be done to alleviate the symptoms.
See Neurologist. Sounds like it is not a hereditary thing, so should get evaluated by a neurologist, particularly if this is relatively new onset or a change.