The electronic throttle assembly may suffer an electrical failure. It is often cheaper to send the valve to a service center for repair that to purchase a new part.Google+
Car Problem Reports
Mercedes-Benz E320 Throttle Valves May Experience Electrical Failure
Mercedes-Benz E320 Problem
Average Mileage: 93,500 mi (85,000 mi - 102,000 mi)
Visitor, 1994 Mercedes-Benz E320, 102,000 mi
Since this description says "electrical failure" I am assuming that it is the widely-reported problem with wiring rather than the resistance element internal to the ETA, which can wear out though not abnormally.
The wiring to the ETA has the same type of biodegradable insulation as the engine wiring harness for these years of production. So if the engine harness is bad, this probably is also. This was the case for me -- the insulation had become brittle and was falling off, causing the cruise control to shut off and cause the ABS and ASR lights to come on. There are a lot of wires in this connection, so there are probably a lot of different failure modes depending on which come in contact!
The ETA are available for under $500 and should be replaced if a car is in the affected model year range. It is important to match the part number as a vehicle with ASR uses a different part than one without ASR.
Visitor, 1995 Mercedes-Benz E320, 85,000 mi
Wouldn't start one morning after sitting for 1 week. Throttle actuator needed to be replaced b/c of degradation.....