Steering flutter is a condition in which the steering wheel oscillates 5 to 15 times per second in the direction of the turn. It occurs at relatively limited but high speeds; generally more than 80 km/h (50 mph), and the oscillations of the steering wheel are fairly constant.
Flutter resembles the vibrations made by an impact wrench when it is being used to tighten nuts.
Main causes
Tire imbalance, run-out, or unevenness
Resonance between the tires and the steering wheel.