Q: Issue with my car stalling - 2003 Chevrolet Malibu

i have a 03 malibu and i have noticed that it has been stalling a lot i got it checked out and they said its the catalytic converter but when I had to get my alternator and battery changed my check engine light went off for about a month and then it came back on and that's when my car started to die a lot and now its worse. sometimes when I start the car it acts like its going to kill but it doesn't but a few mintues later it kills so I have to mess with the fuses in order for it start back up. I have to let the car sit for a while while running in order for the temperature meter to get about halfway before moving the car if not it kills but sometimes when I do that it still kills. I noticed when I first got the car that no matter how much gas I put in the car the needle never goes past the second notch after a half a tank. I really don't know what is going on with the car.

My car has 171200 miles.
My car has an automatic transmission.