If you plug in the charger and it immediately turns on immediately again, then immediately unplug the charger and let it go until it cannot turn on again.
Repeat until it does not immediately come on if you plug in the charger.
I've seen this problem.
The calibration for the battery is off.
Let it bootloop until it won't turn on again.
Then plug in the charger.
If you plug in the charger and it immediately turns on immediately again, then immediately unplug the charger and let it go until it cannot turn on again.
Repeat until it does not immediately come on if you plug in the charger.
Let it charge until full at this state.