97 cavalier has trouble starting

I have a 1997 cavalier that I have had for about two years now and and I have a starting problem that is getting worse and worse. Before when it first started happening the car would turn over but not start only when it was sitting for an hour. If I held the gas pedal down it starts right away and would run normal. Now its to the point where if I hold the pedal down to start it it stalls as soon as I let off and will start right after without touching the pedal. Also the starting problem doesn't happen all the time. Just 50% of the time. I took it to a shop and it wouldn't do anything out of the ordinary and then took it home and it acted up again. I am totally lost and any suggestions would be greatly appreciated. Thank you.

It might be a sensor, and im thinking its the throttle position sensor.