Check engine light code P0172. I have been having the computer reset with oil change place so the check engine light goes off and usually stays off for a long time. Finally, the light came on and then went off by itself. What is the problem or is there not a problem?

The code you mention, P0172 - Fuel Trim Malfunction - System Too Rich (Bank 1)
The engine is a 2.0 lit (4 cylinder). Have you checked to see if the vehicle's powertrain is still under warranty (to include fuel system problems)? If original owner & under 100,000 miles, it may very well be under the powertrain warranty. Check with your nearest Hyundai Dealership & ask the appropriate questions.

My experience with this particular Fuel Trim Malfunction:

1. Clogged engine air filter restricting proper intake air flow
2. Leaky fuel injectors
3. Fuel pressure too high
4. Faulty MAF (Mass Air Flow Meter/Sensor).
5. Faulty TPS (Throttle Position Sensor).
6. Faulty Intake Air Temperature Sensor (IAT)
7. Faulty Engine Coolant Temperature Sensor (ECT).

These causes are only offered as a place to start looking/diagnosing -- NOT intended to cause you to start throwing money after engine parts which may not be the cause -- have it properly diagnosed (probably under warranty).

Hope this helps.