Since two days I also have the issue of random reboots.
Power should be fine, was also no issue the months before.
I already tried a new SD card with a fresh image and my backup, same behaviour.
If I look at the log for the last restart, I see
2022-03-31 12:11:00 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/15d21743_samba_backup/stats request
2022-03-31 12:11:00 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/core_configurator/stats request
2022-03-31 12:11:00 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/core_mosquitto/stats request
2022-03-31 12:11:00 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/a0d7b954_bitwarden/stats request
2022-03-31 12:11:00 WARNING (MainThread) [homeassistant.components.hassio] Can't read Supervisor data:
2022-03-31 12:16:11 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/core_duckdns/stats request
2022-03-31 12:16:11 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/core_mariadb/stats request
2022-03-31 12:16:11 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/core_mosquitto/stats request
2022-03-31 12:16:11 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/a0d7b954_sonweb/stats request
2022-03-31 12:16:11 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/a0d7b954_adguard/stats request
2022-03-31 12:16:11 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/core_configurator/stats request
2022-03-31 12:16:11 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/a0d7b954_nginxproxymanager/stats request
2022-03-31 12:16:11 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/a0d7b954_bitwarden/stats request
2022-03-31 12:16:11 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/15d21743_samba_backup/stats request
2022-03-31 12:16:11 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/core_samba/stats request
2022-03-31 12:16:11 ERROR (MainThread) [homeassistant.components.hassio.handler] Timeout on /addons/core_ssh/stats request
2022-03-31 12:16:11 WARNING (MainThread) [homeassistant.components.hassio] Can't read Supervisor data:
So looks like somehow the supervisor died, and with it all add-ons, leading to a reboot?!
Strange also that first just a few addons timed out, and five minutes later (without any other log entry in between, which usually occur more frequently) basically all…