iPhone 8, although with bad battery health for months - 78%. Had IOS 14.2 like 1 month already. Yet to encounter issue till 4 days ago. Battery were at 70%, and suddenly shut down, restarted and shows 10%. For the past few days my phone had been constantly restarting at least once per day, yesterday the phone was on non-stop auto restart and reboot, stuck on the loading screen for like 1 hour? Before I get my phone to service center for a battery replacement, it auto shut down at 99% charged again. Hope it was just purely battery issue, would like to spent extra on other possible issue.