Hi, don't know if anybody can help with this please.

My Merc ML270 CDi (2000 X reg) sometimes starts and runs okay and when it fancies, on turning the key the dash lights up as normal but will not turn over. Also when it does start and is being driven nearly all the dash lights flash up, the rev counter stops working and it goes into limp mode. Once stopped and able to restart all the lights go out until it decides to do it again, which is quite frequently. No diagnostic faults shown when plugged in. HELP!!

Thanks