You may need a wheel alignment, or you may need bushings.
If it varies with driving speed, look for an out-of-round tire. If it vibrates only when braking, you probably have a warped brake rotor.
This can be a warped rotor or tire out of balance. If it only happens when braking it is a warped rotor.
if it happens when braking, check the stabilizer bolts. both mine were broken
You rotors are warped and will need replaced/resurfaced.
Your power steering pump and or steering box may be about to give out on you.
You have a warped rotor. Brake pads need replacing and the rotors turned or replaced.
Loose or worn steering parts, suspension worn, tires out of balance.
balance your tires
Worn steering or suspension parts. This can be very dangerous, so have this repaired ASAP.
There are several causes of this but the most common we call a head shake. This is when the tires shake side to side, the cure is to insure the steering is tight and you add one or two hydraulic steering dampers.
Brake rotor/rotors are out of round / warped. Check rotors and REPLACE as needed.
Wheels are out of balance