The first step is to open the settings, click on the battery, battery health, and check the battery percentage.
The second step is to use the iPhone normally. Battery health is more than 85% in one year and more than 75% in two years.
Mobile phone system failure.
The third step is to press the power button, slide the screen to turn it off and restart the phone, which can be solved.
Third, the original charger and charging cable are damaged.