Take Larry's advice on checking the lines that pass over the oil filter housing. This happened to me when I was changing my oil once. A line came loose and I could not find where it connected to. After I changed the oil and drove the car, the engine shut off. However, a few hours later I went to a party and I couldn't turn the car off without pressing the manual stop lever. Also, the locks would not work. The next morning, I looked again to find where the mystery line came from, and found that it goes to the injection pump. I plugged it back in and the vacuum system was back to normal. I think the color of the line was blue with a brown stripe, or vice versa.
'82 300D Turbo 215k miles