Zafira intermittently cutting out

[stoo_pid]

We have a Vauxhall Zafira X-reg 2l DTI that has recently developed an intermittent fault, whereby the engine warning light just comes on & the system switches to emergency mode.

It usually occurs when I'm going up a hill but it sometimes happens if I accellerate hard. If I stop the car for a minute & start the engine again everything's back to normal. This can happen anytime from a few minutes into a journey or after a few hours of steady motorway driving & doesn't matter whether it's raining or sunny, warm or cold.

We have always had the car serviced regularly & the fault has been investigated by 3 different mechanics, with diagnostics being run on the ECU, yet no-one can find anything wrong with the car or make the fault appear at will.

Does anyone have any idea what might be the problem? I should point out that I know absolutely nothing about cars, so please assume I'm an idiot!