Some vibration when travelling at 100kph or above.

  mercedes/c-class/1994-2000

I have a 1998 Mercedes C240 W202 Elegance sedan. Yesterday I took it on a freeway for the first time in some 4 months. The engine was at operating temperature, and no warning lights etc. were showing. When I was travelling at 100kph or more, there was a light vibration being felt in the front floor pan (both driver and passenger sides). Reduce speed to under 100kph and the vibration disappears. The car has done 215K's and I am the second owner at 212K's. The service book seems to have been kept up to date, but I wonder about the driveshaft flex joints. Or is there some thing else causing this vibration. There is no vibration felt through the steering wheel. Any help would be greatly appreciated. Many thanks.

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