This sounds real dangerous. How frequently does this happen and does it restart immediately? Has there been a Check Engine Light on? If so the computer in your car will hold important information. If I get a car with intermittent stalling like this I plug in my scan tool and drive the car. When it stalls I look at sensor information data shown on the scan tool. You see a lot of information. I also look at the wiring diagram and connect voltmeter leads to likely problem areas and look at what is or isn't getting power when the car fails. I also T in a fuel pressure gauge and tape it to the windscreen to see if the problem is fuel, ignition or other electrical problems. Sorry I don't know any specific problem with your 740.
I went through this for several months and after replacing the (MAF) Mass air flow sensor that fix my nightmares.even the engine light went off by it self after 7 codes keep comming up just because of the MAF>no more dying on the middle of the autobahn or freeways ,or at stop lights. Good luck guys.