Still happening in 2020. Just got the iPhone 12 last week and was almost done putting all my accounts in. Connected it for charging and an hour later pulled the plug to look something up. Black screen, no reaction, nothing, dead. Connected it to the charger again, bootloop. Apple logo, black screen, apple logo, black screen, apple logo, black screen… Connected it to the old USB A to lightning cable and got it to boot. I was able to do a backup and reset the device that way. Problem is still there. In a few hours I’ll be at the Apple store. … #notamused
If you have the same problem I think the old cable is the only way to get your stuff. USB-C to lightning seems to do something “clever“ that allows the bootloop to happen.