I also observe this strange behavior... as soon as you plug in the charging cable, the pixel tries to boot up, usually shortly after the PIN entry for the SIM card appears, the pixel goes off and boots up again a short time later with the message that the data is corrupted and requests a factory reset or reboot.
Wait a few minutes so that the Pixel has enough power to complete the boot process to the extent that you can enter your PIN and reboot.
Why doesn't anyone come up with the idea of deactivating this "I boot immediately when the cable is plugged in" function?
Can't anyone tell me that this behavior makes sense and contributes to the security of the device if the device is sent into the boot process immediately when it is supplied with power after a battery discharge, even though it is clear that this boot process is unsuccessful?
So forget this factory reset nonsense and just wait a few minutes and boot up.