A shaking car steering wheel is a sign that the tire wheels are bent, the wheel bearings are damaged or the wheels are unbalanced. Other issues could be related to suspension or the brakes.
According to O'Reilly Auto Parts, the most common cause of a shaking steering wheel is a bent tire wheel, which is the probable cause if the shaking happens at high speeds. To diagnose this, the car needs to be elevated and each wheel spun to check for sideways movement.
Wheel bearings can become worn out or damaged, which causes the steering wheel to vibrate. If the wheels move in and out with the car elevated, the wheel bearing needs to be replaced. Rebalancing the wheel system periodically also minimizes the shaking steering wheel.
Other systems can cause the steering wheel to vibrate. If the shocks and struts associated with the suspension system are worn out or damaged, drivers can feel the impact of the road through the steering wheel. Loose or unbalanced steering dampers are another common culprit. If the shaking occurs during braking, though, then the problem could be a warped brake rotor. If this is the case, the steering wheel shakes as the car slows. These problems require a mechanic to repair them.