1995 Ford Thunderbird front end shakes

1995 Ford Thunderbird mileage: 133,000. Since I bought this car in January 1996, I've had nothing but trouble with the front end. I've taken the car to various professionals and not a one of them have been able to fix my problem. The trouble is when driving after a few moments the front end has what I call a steering vibration and the car pulls a little to the right and also feels as though it is going to shake apart. Just yesterday, I had the rotors and brake pads replaced to no avail. It still shakes! I have talked to several people that have the same model car and they all have the same problem. By the way, I have anti-lock brakes. The car will shake and shimmy every few minutes when driving, when it starts to shake I will let off the gas and that seems to help a little. Could my problem be in the steering column or is it the brakes? I don't know too much about car repairs but I do know when something is wrong. Another thing when the car starts to vibrate no warning lights of any kind come on.