inner ear infection
, middle ear
/eustachian tube problem, sinus infection, or allergies are the most likely culprits. other causes could be cholesteatoma, vertical heterophoria syndrome, tmj(jaw problem), neck problem, perilymph fistula, or a pinched vestibular nerve. other more serious, but far less likely causes are unstable blood pressure, brain tumor, nutrient deficiency, or an auto-immune disease. do you work with doctors? ask them or make an appointment with one.