I had a similar issue and fortunately the reason was simple for me. The metal piece that goes over the battery and holds it in place was loose. While driving it would sometimes slide and make contact with the positive terminal (thus causing a short circuit, since the metal piece is connected to the body and hence grounded). When this happened, all electrical systems would shut down, navigation display would flicker etc. This only happened while taking a turn (hence sliding of the metal piece) and then everything came back to normal.
Based on my experience, I think something is causing a short circuit in your car.