Cold Starts

When the temperature is below 45 degrees or so, my 96 Grand Am GT 3.1 ltr V6 appears to load up during initial start up, so occasionally I have to depress the accelerator about a 1/2 inch while cranking and then it starts fine and runs fine there after. Its only when its cold outside and the car has been parked for more than 5 hours or so, it will have a rough start. Does anyone know what might cause this problem?