I'm not sure if it is this, but this, sort of, happened to me but it was sudden on my old 155 v6.
The crank or cam sensors are prime suspect, but crank mainly. Get them tested manually, (old fashioned way - voltmeter and oscilloscope if required - the info is in the autodata CD's and books)
What happened to mine was it tested out ok by the ecu but the voltage dropped when being cranked - not a spark or fuel injected as the ecu has no idea where it is. So it does teh safest thing - nothing - it has no idea the engine is turning! It's about 4.2 volts or something ign on - but mine was dropping to 3 volts when cranked. New crank and cam sensors and it fired right up (this was 2 months after), literally, the starter turned the engine onto the 3rd compression and away she went.
Don't trust fault readers - just cos they say there's no fault doesn't mean there isn't one. Use them first then go old scool with voltmeters and probes - you will find the fault if you know how to look!
Hope that helps, just had to share as i know how it is when everyone looks bewildered and it's your car not working!
We have no plan, therefore nothing can go wrong (much)
And i Have finally put piccies of the silver one on!!