I had that issue with a Sony TV and a Sonos Arc ( not Ultra ).  I turned off TV Autoplay in the Sonos app and disabled all Voice Control options.  On the Sony TV I disabled the WiFi connection ( My Firestick does all the apps ).  I Don’t have a clue which one fixed the issue as I did them all at the same time.  Don’t know if any of those changes would work for you.  So far the TV here has not turned on by itself in around a month.

Thank you for your answer. I have already tried the things you wrote, but it’s not working. Maybe I should reset my tv or soundbar, no idea. Any more ideas ???

Are any other devices, such as a cable box, connected to the TV?

What happens if you disconnect the devices to your ‘other’ TV HDMI ports, leaving just the soundbar connected to the TV? I’d see if that might cause the issue to go away too.

Yes, there are cable box and ps5 connected to the tv

I can disconnect the other devices, but what if it helps . But I will try

My thoughts here are to find which ‘other’ CEC enabled device (PS5/Cable-TV) is perhaps causing the issue (rather than it perhaps being the soundbar) and then go onto see what happens if you go onto switch off CEC in the settings on that device, but first, you need to see if it is resolved by removing one of those ‘other’ HDMI connected devices first.