White dots can be seen on the black screen when turning on the TV after being in a cold place for a long time.

This is not a malfunction but a result of the Liquid Crystal material changing state after a long time at very extreme low temperatures, such as in the winter.
The Liquid Crystal material will return to a normal state after operating the TV in an environment where the temperature is more than 10℃ (at least 5 hours is recommended).