Please help! Need a diagnosis for an engine problem...

This problem has happened to me twice so far and it seems to occur when I haven't driven the car for an extended period of time (like 9+ hours). I will go to start the car and it will turn on and turn over the engine just fine but as the rpms go way up on the start the engine will not catch idle on the way back down, it just turns off. Then I can probably keep trying to start the car normally with the same results. BUT if I give it lots of gas as it's starting up (when the rpms are going up for the first time) it will go back to normal and hit regular idle rpm. The car will also drive normally. It's so weird. Both times when I left the car it was fairly humid outside, maybe that has something to do with it? The first time I drove my car to work (6am) and didn't try to start it until about 4 in the afternoon and it just happened again yesterday. I drove my car to work at about 8 in the morning, friends met me at work and we went downtown chicago until about 12am so I didn't start it for a pretty long time. I have also never had this problem when the car sits overnight. Strange.

Anybody have any idea? Any input would be helpful

No one knows what it could be?????