car just stopped running in driveway

I never have had any problems since I've had this car from the first day as a new car as for as gas mileage or acceleration, etc. but, today I had made a few errons about town and was going to put the car back in the garage when I got out to open the garage door and came back and opened the car door I started to get in when the car just stopped runnig. I turned the key to the off position and then back to start the car and it started right up. Now as I was getting into the car I did nothing to me knowage that would cause this car to shut down. I'v run this car on this tank of gas down to a quarter of tank of gas with no indication that the gas is or was bad and this gas has only been in the tank for about three weeks...