I have a 91 190e 2.3L. Recently the steering wheel has been shaking violently (left to right) when driving at high speeds (60mph). It's most common when going up hill while braking. It does not always happen. Sometimes it will start and then stop and ill never have a problem with it again that day. Other days it wont happen at all. I checked the rotors and they look good and straight, brake pads are all new. Tires are old but have at least 2 months left of life. I am thinking it is something in the steering or in the suspension. Any ideas?

Andrew

 

check those tires again...they're size (offset, amount of thread) might be throwing the car off.

 

60mph = High speed. Not over here!
I suspect the key word in your description is uphill. If so this might suggest your lower ball joints are shot since weight is transferred to the rear whilst going uphill. Any lateral input run out or thick thin from the brakes will become more apparent. How have you checked the brake rotors for runout? Only way to get access top the rotor surface is with the wheels off and it is then necessary to have a dummy small wheel to clamp the brake rotor to the hub whilst you observe/measure run out.
My guess is bad rotors accentuated by the lower ball joints.
Vehicle mileage?
Hope this gives you some ideas.
Stuart