My car occasionally cuts off when coming to a stop.

My 2003 volvo s60 occasionally cuts off when I come to a complete stop. The car will immediately crank back up as if nothing were wrong. Normally, the rpms will briefly drop close to 500 when stopped and then come back to about 750. On the occasions when the car cuts off, instead of returning to 750, the rpms drop a little below 500 and then the engine cuts off. I've noticed that this situation happens in cool/cold weather. It started in early spring (one occurance). Did not happen at all during the summer or early fall. Once the weather starting getting cold again it starts randomly happening again. No check engine light comes on. Car seems to run normally otherwise. Has happened with the defroster on but also has happened with only the heater on. Thanks for your helop