hi my 1985 500sel v8 runs perfect when cold but after about ten-=fifteen mins it starts to misfire realy bad switch off for about 5mins and it will run perfect for a small while then the same again changed coil but no good leads seem to be fine new a few years ago but has only done 600miles as been off road for 7yrs any help pls

 

MAybe a valve is sticking closed when it gets hot. I dont want to lead you in the wrong direction though. Check the basics first like coil wires, spark plugs, cap and rotors, ect..