I have a 2000 A140. It used to not start periodically. Now it wont start at all. By 'start' I mean no ignition, no dash lights (except SRS airbag).
Is this an immobiliser problem. There is a Relay called 'starter lockout relay', I presume this is the immobiliser section. Intermittent problems can be faulty relays.....
I had a similar problem, car was showing a start error and then engine went dead. Brought car to merc garage they put it in test mode and found my key was faulty. Key had become altered from a another key that caused a fault in the chip reader. Changed key and presto problem gone.