I've got a new X-cover5. I charged it to 40% at lunchtime then plugged it in again overnight. In the middle of the night it made a persistent warning noise. The screen was full of small text that began "unplug the charger immediately" so I did that and the message disappeared, and the noise stopped. I'm aware that overheating can be a problem so I felt the phone and it was not hot. What can I do to avoid being waken up again?