Car not starting intermittently

Bought the car when 3 years old with low mileage. After ten months while driving a red flashing light came on the dash(usually when its been raining). When engine is switched off it then won't restart. It's had a new starter motor, and a new ecu. The garage says it's coming up with a couple of error messages but none relating to non starting. It failed to start again last month but by the time the garage could look at it, it had started again so they couldn't find the fault. Any one else had similar issues?