Here are the known facts:
1) When driving from 5mpg-55mph the steering is ok but feels a little wobbly
2) At around 60-75 the steering gets violently wobbly
3) This does not happens every time I'm over 65 but most times
4) Sometimes when I hit the brakes a little it subsides
5) I do not think it is a wheel balance issue because I never saw any weights on that tire/wheel.
6) I took the tire off and tried turning the wheel by hand. It turns freely for about 75% of the rotation and then seems to grip on about 25% of the rotation making me strain harder to turn the wheel.
7) Recently when I first start the car and I put my foot on the break the brake pad sensor light goes on but it goes off when I release the brake and doesnt usually come on when I'm driving.

I'm planning on selling this car this month so I dont want to waste a bunch of money fixing the wrong problem. Other than this the car runs perfectly.
Please help me!

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1993 Benz-190E-2.6 liter