It sounds like it could be something in the ecu that expands and disconnects, Then cools down and reconnects like a crack in a circuit board or something on those lines. Just a guess, I had a car back in the 80's that did this and it reminds me of my few times going down the road then WHAM totally off, disconnected, shutdown. 5 min. later it would start and I never knew when it would happen again.