I agree that Mercedes, and also BMW, feel better as road speed increases. When I was much younger I bought a new BMW 2002 in 1971. It was more comfortable at 75mph than at 55. Many of us remember President Nixon's mandate to reduce the national speed limit to 55. My 94 E320, which I have owned just one month has the same characteristic - the faster it runs, the better it feels.
regards,
Mark