Why would your steering wheel shake?

A shaking steering wheel can indicate many things, most of which are related to the tires of the vehicle.

It could mean that a tire was not held flush to the wheel the last time it was changed, which could be corrected just by reapplying that tire correctly.

It might also indicate a tire rim is bent, which you can check by jacking up the vehicle, spinning each wheel by hand, and checking to be sure that each tire spins straight. If any sideways motion, the tire should be replaced.

If it only happens at average highway speeds or higher (not low speeds), it might indicate tires are out of balance, which is due to some having more wear than others. A professional tire rotation can be done to correct this, and tires that are too worn, leaving inadequate tread depth, should be replaced.

Another and more serious cause of a steering wheel shaking, or if the car itself seem like it's bouncing, could be a faulty tire, in which the tread piece (the portion that touches the ground) is no longer fully attached to the base or sidewalls. This should be corrected with tire replacement quickly because of the dangers of accidents and loss of vehicle control that can be caused by losing a tire tread while the vehicle is in motion.

If the steering wheel shakes only while braking, that would indicate a problem with the rotors of the vehicle, in which one of the rotors was mounted tighter than others. Correcting that problem would require professional mechanical service.

If the rate of shaking increases as the speed of the car increases, it could mean problems with other parts of the vehicle, such as need for replacement of the ball joints, tie rods, upper strut bearings, or shock absorbers.