2002 Cadillac Deville

My cars stalls about once a week.... BUT only at stop lights or stop signs. I suspect the idle control valve is unstable... or the throttle postion sensor is acting up. How can I tell which it might be. I did clean the throttle body and still stalls. NOTE: once it stalls it is a bit hard to start unless I press on the gas just a little. Then when it starts, it is not a problem for another week. Also it only stalls shortly after starting the car on the morning OR when i start the car and go home and it ALWAYS stalls at stoplights in LESS THAN 5 mins. It never stalls when the engine is hot ( say running over 10 minutes). MANY THANKS !