I have a problem with my 320 SLK in as much as some times I can turn the ign key and nothing happens then go away and then it will start - no noises from starter etc or dimming of lights just dead yet I have squirted a PTFE spray in the key hole and it will work. Just picking it up from the local Merc dealer and they cant get it to fail obviously cannot fit any parts, so any ideas would be grateful.