You may not have made any network changes, but that doesn’t mean that changes haven’t been made internally, with updates to your router’s firmware, or an impact from external wifi interference.
There are a couple of possibilities that come to mind, that might cause your device to be rebooting, which is a guess, based on your post. While it could be a network issue, it also could possibly a heat related issue, or an issue with your TV sending a ‘bad’ signal that the Sonos isn’t able to interpret.
I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. But don’t post the resulting diagnostic number here, they get sensitive about GDPR.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.
Have you fully inserted the power cord into the Arc?
Many folks have been afraid to push hard enough to fully seat it.
