Try force restarting your device the steps below are as follows to do so:
On an iPhone 8 Plus: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then, press and hold the Side button until you see the Apple logo.
Side button is another word for power button.
Basically press volume up first, then press volume down, then you press and hold power button until you see apple logo like 10-15 seconds.
If that doesn't work then I would assume there is an issue with the hardware inside the phone which then I recommend taking it to a reputable phone repair shop to check what's wrong with the phone. Hopefully just the screen or a loose connection.
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2
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And my phone was 80% charged.
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