Because almost every motor in a car automatically reset […]
Because almost every motor in a car automatically resets its internal overload protection in the form of a bimetal circuit breaker (older mechanical technology) or a PTC (Positive Temperature Coefficient) device. This is in addition to "slow-melt" fuses used in circuits that power electric motors. Sometimes you can see / feel this internal circuit breaker at work, for example, when the side window is frozen closed. If you keep trying to cycle the window open, eventually it will overload and stop powering the motor until it cools down enough to reset.
The best way is to apply some de-icing agent, then remove it from the windshield, then open it, and then de-icing it.
If there is no deicer, start the car and heat it with a blower on the windshield until you get some hot air, then remove as much ice as possible by hand, and then release the wiper from the screen again.