TDCi Fords had quite a lot of engine management problems which have been rectified on the later models. When it happens again take it straight to a Ford dealer for diagnosis as apparently after starting/switching off the car ten times after the problem it clears the memory, hence there being no record of the fault. If the car is still under a Ford warranty, don't give up until the problem is sorted as they will (if necessary) replace the engine management system.
Yes, I've had (lots) of similar problems with my '02 plate TDCi Mondeo (brilliant car in every other respect though).