Check out how to force restart Android 9.0 Pie. As a result your HUAWEI Mate 20 Pro should reboot and start running again. Click here to find out more about soft reset operation. How to soft reset HUAWEI Mate 20 Pro? Hold down the Power button for a short while. Then from the menu choose Power Off and tap OK. After that wait for a short while.
The ambient temperature is too low: Prolonged use in extremely low ambient temperatures will trigger your phone's low temperature protection mechanism, causing your phone to power off or restart itself. Abnormally low ambient temperatures can also decrease the chemical activity of the battery and reduce the battery lifespan.