try swapping the relay with another and see if it fits tighter. if not, you maybe to to modify the socket a bit by trying to tighten the connectors that attach to the relay.
It may also be a loose wire in the wiring area below the relay
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.