Somebody correct me if I am wrong, but I don't think that warped rotors would cause a vibration with out the brakes applied, and even if they somehow did, the vibration would get worse when the brakes were applied.

It sounds like um-balanced/out of round tires to me.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine