This is strange, try these steps and see if it works:
Soft Reset: You mentioned that the phone came back to normal after holding down the power button for over 10 seconds. This is known as a soft reset or a force restart, and it can resolve temporary glitches in the phone's software. If the issue resurfaces, you can try performing a soft reset again to see if it helps.

Check Charging Port and Cable: Ensure that the charging port on the phone is clean and free from any debris. Sometimes, dust or lint can accumulate, preventing proper charging. Additionally, try using different charging cables and adapters to eliminate the possibility of a faulty charger.

Factory Reset: If the problem persists, you might consider performing a factory reset on the phone. However, keep in mind that a factory reset erases all data on the device, so it's crucial to back up any important files before proceeding. This step can help eliminate software-related issues that may be causing the problem.

Contact Customer Support: If the issue continues to occur or if you're unsure about performing troubleshooting steps yourself, it's recommended to reach out to Tecno's customer support or take the phone to an authorized service center. They can provide specialized assistance and diagnose any underlying hardware or software problems.