After being enabled, the personal hotspot may turn off automatically and a message displayed in the notification bar warns you that the Wi-Fi hotspot has been disabled.

This is normal and it does not mean that there is an issue with your device.

In order to extend the battery life, the system automatically turns off the personal hotspot if no device was connected to it within 10 minutes after the hotspot was enabled (2 minutes for device running EMUI 8.X and below).

This feature cannot be turned off temporary. If the device is charging, the personal hotspot will not be disabled automatically.