It might have been since the update to Oreo or just coincidence but my phone started rebooting by itself. Also noticed when it reboots after doing the usual booting animation which takes much longer than usual it will ask for unlock pattern and do the boot animation again. I notice sometimes after reboot the phone feels weird, a bit sluggish and some apps don't work properly. For example anything that calls the camera will say it is not available. Other things like for example VoIP features in messaging app won't work. Another reboot would fix the issue or it would stay the same and require another reboot. This issue got worse and worse where it would require multiple reboots or take longer and longer for the reboot sometimes just switching off during the reboot.
Of course I tried wiling cache. Didn't help. I wiped the phone and gave it to my mom and it seemed to fix it at first. It started appearing again eventually. So I see multiple possibilities.
- Rogue app. But my mom has only a few apps, different from what I used.
- OS update messed up? Phone is currently on latest OTA on Pie. Would a custom rom help?
- Battery issue? This would be simple to fix but the phone rebooted regardless of charge state, once I saw it even doing so while hooked up. I didn't observe a drop in charge after reboot either.
- Mainboard / Nand issue.