What makes a car vibrate when driving on the road?

If it is something that you can feel through the steering wheel, and it either gets worse as you pick up speed or kicks in regularly around the same speed, then your front wheels are probably out of balance. Maybe you had new tire or tires put on and they weren't balanced by whoever put the new tires on. Take it to Pep Boys or a tire dealership and ask them to balance the front wheels; it's not that expensive, and it's cheaper than my other idea, which is your motor mounts are shot or, even worse, your flywheel is out of balance. But, in my experience, it's always been the wheels out of balance. Phil