hi. needed help fast!

i was driving on my way to the office. ok, ganda ng takbo ng car. then i have to stop over to a gas station to refuel. there i have to turn the engine off. upon starting again, i noticed that my idling is dropping until i reached the parking lot. so, turned the engine off and was about to leave. curiousity, i tried re-starting the car again and it started naman but namamatay agad.

how can i resolve this problem? what would be the cause?
thanks.