Check for vibration at the drive tunnel at about the rear of the front seats. If you feel vibration here, it's almost certainly the driveshaft, and I would expect it to be flex disks. Usually the center carrier will be worse on acceleration or deceleration, on coast it will disappear sometimes. If the vibration is centered somewhere else, it's not the driveshaft.

Raising the tire pressure can cause a bad tire to vibrate more -- check for "snaking" treads or blisters on the tread, and spots more worn that others.

Flex disk replacement doesn't require separating the two halves of the driveshaft, but center carrier does. Mark before pulling them apart, Benz doesn't use a blind spline like Volvo does (very nice, impossible to get it wrong as it will only go together in the correct spot). Clean and use a paint marker, and allow the pain to dry before pulling them apart, you will be very unhappy if the marks get wiped off somehow.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!