'95 E420 - Vibrations in Steering Wheel at Idle

Hi,

I've spent about 6 hours going through all the posts trying to coming up with a short list of possible causes, but I haven't found any posts describing a similar problem. So, here is goes...

Before this started, if the car was in Drive or Park, you barely knew if the car was on. There were no vibrations in the cabin nor the steering wheel.

When in drive or park, there is a vibration easily felt through the steering wheel. It has varying degrees. Sometimes you it is not there at all (about 5% of the time). Most of the time it is noticeable has oscillates from not too bad to very noticeable in 2 second intervals (think of a sine wave). Other times it is much more noticeable and can be felt in the seats, gear selector and you can hear it too - like the timing is off and exhaust has more of thumping sound.

Often when coming to a stop at a red light, the first couple of seconds, there are no vibrations. After a couple of seconds the the oscillation cycle starts.

On occasion (maybe every 4 to 6 weeks) the cars shakes alot when first started - this last for 30 seconds at the most. Happens more frequently when it is cold outside.

Electrical load makes a difference for a couple of seconds - for example, if all the electrics are off and then I flip on fan, then headlights, then stereo, etc. there is a spike in the vibrations, but the goes back to the usual range of vibration after about 2 seconds.

If you are really tuned into the vibration, you can feel it in nuetral or park, but it's much less than if the car is in Drive or Reverse. It's very faint in park or nuetral, but the car goes from vibration to a subtle rock or kick every couple of seconds. Put the car in drive and it sounds like you put front wheel drive 4 cycle japanese econo-box into drive.

The car has 95k miles; at 86k miles (Nov. '91) it had the transmission replaced and motor mounts. The vibrations were occurring before this repair and continued afterwards. At 90k miles it had its schedule service. Every 2 to 3k miles it gets a bottle of techron.

I bought the car about 2 years ago and did NOT have any of these vibrations. they started last summer and have gotten alittle worse - meaning, occurring on a more regular basis, but but the range of the vibration is about the same.

Seeking suggestions and order to ruling out causes - I don't want to spend $2k only to find out a $50 part replaced at the started would have solved it all!

Thank you very much for your input. John.