odd vibration in gas peddle of 420sel

[carl rast]

I have searched the forum and found no post to resolve this problem. i would appreciate any help. I have for a long time had a intermittant problem with my 1990 420SEL. The gas peddle vibrates with a high frequence vibration when I lightly depressed. The problem has become more noticable and last long enough to get the car home. I now find that I can feel the vibration throughout the engine compartment at idle and that it quits when I shift to park. This is a high frequency vibration almost like a massager. I have searched and posted on other forums and find others say they have the same problem so it may be common to the 126. Hope someone can help. Thanks