What's wrong with my car

What is your question?

While I was driving down the high way my cars speed stated to decrease rapidly, it completly stopped, as I was stepping on the gas petal!! When I tried to start it, it would not start back up at all!! A week before that it over heated but once I turned the car off then back on it worked fine...can someone plz help and explain what happen??..I need a car and need to know what's going on