94 Buick Century

When I start my car in the mornings with temperatures normally anywhere from 50-60 degrees it always shuts off after a couple of minutes of me trying to let it warm up before I began to drive to work. I always have to restart it. The only way for it to stay started while trying to warm up is when I put my feet on the gas for a few seconds everytime I feel its about to shut off and thats when the car stays on. But I can just start up the car and drive off but it should warm up to temperature before I drive it.