Last week while driving on freeway gas gauge suddenly dropped to 0. Minutes before it had been near 1/2. I stopped at next gas station did several key switches and it stayed at 0. Decided to fill up and go by trip odometer until I could get into dealership. It only took 8 gallons to fill. About 2 hours later stopped for lunch. On restart gauge function returned to normal. It's been OK now for a week. No point in taking to dealer if it's working. Any ideas on what hsppened?