Our 2004 sonata 4 cdylinder starts up and then 2-5 seconds quits. It will not stay running.

What is the repair history of this car? Any recent repairs? New keys, etc?
Does this car have an anti-theft system, original or aftermarket?
When it quits, does it lose fuel or spark?

Check for codes. I'd focus on the Crankshaft Position Sensor and the Camshaft Position Sensor.