It is the Mercedes-Benz engine and motor mounts that hold your power plant in place under the hood of your vehicle. These have both polymer and metal components to them, and it is usually the polymer portion that will wear out in time requiring it to be replaced. The reason there is both metal and polymer portions of the engine and motor mounts is to help cushion the vibration and movement of the engine so the passengers and drivers will not feel it. This way a smoother ride can be felt by those that travel in your Mercedes-Benz. There are a total of between three and five engine and motor mounts on most vehicles manufactured by Mercedes-Benz. There is one on each side of the engine near the middle of the engine block. There is a third one located in the rear near the transmission. Finally, there will be another one or two mounts at the front. This multi-point connection cushions the torque the motor generates and holds the engine in place. The most common engine and motor mount that fails is the one located on the driver's side of the Mercedes-Benz engine. This occurs because of the nature in the way the engine is twisted when it is running by the torque being generated. This torque is from the spinning of the crankshaft in the engine. To inspect the condition of the engine and motor mounts can be done visually by crawling under the car. It can also be noticed by revving the engine up and noticing just how much movement the engine has. If the motor moves noticeably upward then the Mercedes-Benz engine and motor mounts are beginning to fail and they should be visually inspected and replaced.