I left my phone charging overnight, and in the morning I woke up and the phone was stuck in bootloop. The Apple logo came on, then the screen turned white, sometimes with 1 black horizontal line or sometimes a pixel (greenish).
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While the screen is white I would try force restarting.
If that doesn't work, and you have a computer and some time, I would force it into DFU mode and restore it with iTunes.
HOWEVER, do not use DFU mode if you do not have a backup of the phone. In that case, I would take it to the nearest Apple Store and ask how they would suggest recovering your data.
