If you’ve already power cycled the Arc, and checked for firmware updates in the Sonos controller, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. 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.

Thank you for your comment 

I talk to Sonos support a couple weeks ago about a solution 

the solution was to reboot my arc.

after I rebooted the arc it worked but now the problem seems to start all over again 

I will call Sonos tomorrow 

thank you

I’m not familiar with this issue, it doesn’t occur on either Arc I own, so I’m just not sure what might be causing it. Sonos support gets a much wider view of reported issues and potential solutions. 

So you are saying that the “physical” switch on the back of the Arc Ultra is moving between on and off? That's really weird.

The only other way to disengage the “mic” is via a “soft” shut-off on top of the Arc Ultra. That really only stops the voice assistant (Alexa or Sonos Voice) from recognizing/responding to a command. Assuming you have one or both setup on the Arc Ultra.