First time happened about 3 weeks ago, got in the car, turned the key and it started for about a second then stopped. Turned key off then on again but this resulted in the engine turning over and not starting. Left it doing this for about 6 seconds then switched off and tried again, think it started after a couple more tries. Didn't think much of it at the time but last week after I started the car and moved forward 3 car lengths, the engine died. I was in a car park and ended up embarrassingly pushing it to one side as I was blocking the entrance. This time it would not start and just kept turning over. After about 15 minutes and me wiggling the Brabus connectors the car started. Booked in to merc this Saturday to see what they thought. Yesterday though for the first time the car actually died whilst I was driving it. Not a great experience but luckily I wasn't driving it fast! Just about to turn into a junction but had to abort and drove straight across the junction in front of a van and then up the pavement! Van driver not impressed but I gave him the universal shrug for my car is broken! Turned ignition off then on and it started straight away. Drove it for another 5 minutes and it cut out behind a bus yet again! Took it into merc today and unbelievably there were no errors codes in the system. I am sort of thinking that maybe the Brabus chip is at fault but merc did call back and said they haven't been able to replicate the engine failing but would keep it until Monday and change the crankshaft sensor anyway. Any thoughts? After scouring the forum it would seem this could be at fault but if it was why didn't it generate a fault code?