PT Cruiser losing all electrical power

My daughter’s 2003 PT cruiser shuts completely down a couple of times a week while driving or stopping at the light but it starts back up when we start it. I figure there is a loose connection ro something but I can’t figure out what it is ans how to find it. We took the car to the dealer and they didn’t find anything as it is an intermittent issue. Any clues on what I should do?

I would start with the ignition switch. Try tapping on suspected areas to search for a bad connection while the engine is running.