akathisia

Literally, inability to remain motionless. A side effect of certain psychiatric drugs that can be a mild sense of disquiet or anxiety (which may be easily overlooked) to a total inability to sit still, accompanied by overwhelming anxiety, malaise, and severe dysphoria (manifesting as an almost indescribable sense of terror and doom). - wikipedia Often accompanied by dyskinesia, or tremor. Contrary to the other definition, it IS treatable.