On four separate occasions now, while driving, the vehicle has completely shutdown. Two times this has happened in a parking lot and was relatively safe when it happened, but the other two times have been while driving on the freeway at freeway speeds. On all occasions, the entire dash will flicker a couple times, while the engine will sputter and then shut off. When this happens ALL systems including brakes, dashboard, engine, and steering are completely inoperable. Twice this has happened on the freeway while moving at freeway speeds. Thankfully, on neither occasion did any accidents or injuries occur, but it could very well have been fatal. On all occasions, the car will remain off and cannot be started again by pushing the ignition button for a period of about 20 to 30 seconds, during which time I cannot steer or stop the vehicle. After about 20 to 30 seconds, the car will turn back on and appear to function normally.