Engine Shut Off Without Warning problems of the 2009 Hyundai Genesis

My car shut off/the engine lost power, while sitting in traffic. I felt a slight rough idle, then realized all my dash lights were on, and the engine was not running. I placed the car in park, and pushed the engine start button. Car started back up, but every time I stopped I had to place the car in park and keep my foot slightly on the gas to keep it from idling roughly and shutting off again. I had to do this for a half hour until I reached my destination. After setting for 4 hours the car started fine and I had not further issues. But my fear is that it will happen again while in traffic or possibly while driving, which could cause an accident.

Engine just shuts off while driving. It becomes difficult to steer and control. I was barely able to move to the side of the street and the car behind me almost ran into me because of my loss of power. There are no warning lights and the radio, etc. All stayed on during this event. I had to put the car in park and restart the engine.