1997 Pontiac Bonneville Stalling

Car generally runs great, but will occasionally stall while idling (whether it be at a full stop or even traveling down the freeway with my foot off the gas), or try to stall while accellerating (engine will shut down for a second then kick back on again if my foot remains on the pedal). Usually starts back up right away, but sometimes requires a couple mintue's rest before starting. Been going on for months now, no codes, getting progressively worse (3-10 times a week). Have replaced IAC, TPS, checked all vaccum hoses, and have cleaned the throttle body. Any ideas on what else could be causing this?