Stuck in fastboot mode

Search came up with:

How do I get out of fastboot mode?

Press and hold the power button or power key continuously for fifteen seconds to fix Android stuck on fastboot mode. Your Android device will vibrate once and then restart. In some phones, you might need to hold the power and volume down button simultaneously to restart.

and

remove the battery, wait 5, reinsert and switch on.

if no removable battery, then complete discharge to get it to power off. Then connect charger, turn back on.

These are ways of restarting the device, it seems the main thing is to restart it.