I had that problem on my old mondeo, I never got it checked out till it died and wouldn't restart. My car only did it on motorways at 70+ under load. I had a cam sensor changed and it stopped it for a while (say 5000 miles) and then restarted the cutting out. I never got to the problem as the car was then traded in for a new shape mondeo, the car had done 260,000 miles and wasn't worth messing about with.

It's worth checking the cam sensor.