Why a car shakes when it drives?

Answer 1

Typically it means that SOMETHING is "out of balance", and when a wheel, tire, shaft or other spinning component moves, the balance issue is greatly accentuated.

In order of probability:

# Tires are out of balance # Wheel is bent # Drive shaft or "Half shaft" is bent or a bearing or u-joint is worn. However...

if the shaking only occurs when you touch the brakes, it's probably a warped brake rotor, which is a common cause of shaking, especially in the steering wheel.

Some people will tell you that the shaking is caused by a worn suspension part or worn shock absorbers, but if everything is balanced properly, neither of those two problems will CAUSE the shaking, they will, however, make the shaking worse if there are other balance issues.