A few months ago, I was driving on the highway, in heavier traffic so my speed was varying a bit. All of a sudden my steering wheel starts shaking so violently, I had to pull over. After I pulled over, and took off again on the highway, no problem. This problem has progressed. My steering wheel shakes randomly, but now my gas pedal has a vibration when going anywhere between 55-70 mph. And the steering wheel shakes violently at the same speeds randomly. I took it into the dealership twice now. The first time they balanced my tires... didn't fix it. The second time they did a recall for my car on power steering issues. Didn't fix it. I had my brakes checked, tires balanced yet again, and no one can tell me what the problem is. Can you help?