How much RAM do you have? I upgraded a couple of laptops to windows 11, and they can’t accept more than 4 gigs. They run very slowly. How much free disk space is there?
The rebooting, closing files, and loss of audio sounds more like bugs than malware. Low memory is certainly a plausible possibility. Open Task Manager and see what it says about your memory usage.
But if you want to double-check for malware, I’d try Bitdefender. I’ve had Bitdefender detect problems that weren’t detected by MalwareBytes.
I can’t completely rule out malware based on what you have posted, but these two in particular seem like failing hardware or driver bugs.
Check your settings to see if you didn’t accidentally add a filter of some sort (settings → see all settings → filters and blocked addresses). Also check your settings for labels and make sure you aren’t accidentally hiding things there either. A third thing to check is your spam folder. I had to make a filter for one particular sender because gmail was somehow convinced that they were a spammer. I had to set up a “never send to spam” filter for their email address.
What happens if you use a clean browser (not Chrome) and open a Netflix video?
Rebooting without any messages sounds like a temperature problem. Try to find out your cpu/hdd/RAM temperatures directly after booting and after a reasonable amount of use/time.
You could also try to find the cause of the reboot in the logs.
There are a few online free scan tools from reputable companies. (Trend’s Housecall comes to mind) Free and cheap peace of mind to see if they can find any problems.
I was having a mystery reboot, and it turned out to need an updated driver. If you are techie enough, you can look for messages right before the reboot, and then google any suspicious messages. It gave me the hint that it was the video driver.
Here’s one of many tutorials about how to read the event log: https://www.tenforums.com/tutorials/78335-read-shutdown-logs-event-viewer-windows.html