Work through these checks in order
Connect to a reliable compatible charger and give the device time.
If the device is hot, stop repeated restarts and allow it to return to normal temperature.
Follow the model-specific sequence once rather than repeatedly pressing random buttons.
If a computer-based recovery mode offers an update before a full restore, understand the difference before continuing.
A restore can erase the device. Do not proceed unless you understand the consequence and backup situation.
Before an erase, restore or repair decision
Confirm what data is backed up, what a reset or restore will remove, and whether you still need access to account credentials or authentication methods stored on the device.
When professional service makes sense
Hardware damage, repeated power failure, liquid exposure, battery swelling, damaged ports, broken displays and problems that persist after low-risk software checks can require qualified inspection.