flushing your engine with an over the counter engine flush and then change your oil. Sometimes sludge will build up in the engine and since the oil sender unit comes in contact with your oil... Please note that MB does not recommend engine flush but, it worked for me. However, my symptoms were different. Low oil level light on when turning (specially to the left) and oil pressure gauge would fluctuate. Obviously, before you do this, check ALL your connections.
By the way, were you driving in a straigh line when you noticed this? ANy warning lights on in the instrument cluster?