I have this problem with my 95 S500 which the dealer can't seem to fix. When the engine is idling I feel a very slight vibration. It feels as if the engine is mis firing because the vibraion is not constant , but you could feel a slight shaking or shudder as the engine idles. It is not a very noticeable shaking or shuddering but I am very sensitive to it and that is why I would like to correct the problem. The dealer have so far replaced the engine mounts, Distributor cap and rotor and reset engine computer. They have also told me the service rep has checked the car and the shaking is not excessive and within the norm. Any possible solution to this problem would be greatly appreciated.