A while back, M-B had a lot of consumer complaints with the W140 chassis and tire/wheel vibration. The M-B dealer in Tiverton, Rhode Island was doing a service on my 190E 2.3-16 about ten years ago, and he talked me into using the tire balancer M-B prescribed for resolving the W140 series issues. It involves balancing the tire/wheel assembly while it is mounted on the car, and I was impressed enough with the way the tires just stayed stuck on the ground with no vibration that I went back to have it done again when the tires were replaced. If they were closer, I would do the tire service there all the time as there was clearly a difference (improvement).
I would expect a driveshaft balance problem to be accompanied by some noise, also related to the rotational speed of the driveshaft which is around three times as fast (three times the frequency) of the wheels. So your vibration sensation would be pretty high frequency at 150-170 kph.
Hope this helps, and good luck. Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)