Most likely the wheels and tires are not properly balanced... could also be something loose in front suspension.
who is this and then i will tell you
Motor is idling rough.
Tire out of balance, loose lug nuts, worn wheel bearing, or bent wheel.
Most likely warped brake discs
If it shakes all the time it is a tire/wheel problem. If it only shakes when braking then it is a brake problem.
Losse wheel, worn bearing, or more than likely, a worn CV joint.
Tire out of balance, bent wheel, or if it vibrates only when braking you have a warped rotor.
Check your power steering fliud, if it is low this could cause the vibration you are feeling.
Not surprisingly, it depends, if the steering wheel vibrates all the time, no. IT could be a whole bunch of things. If it just vibrates at a certain speed range, roughly 50 to 70 mph, it is probably the tracking on your tires (or at least that's worth checking as it is a cheap procedure). Either way, if it makes you feel unsafe whilst driving the car, then don't drive it.
bearings inside your sterring colum need replacing
maybe the car need to be linged up n check the power steering.
sitting and idling ?possible bad engine or trans mounthave them inspected