When you ran First Aid, did you run it on the hidden Container? And did you click the "Show Details" button to scroll through the report to see if any unfixed errors were listed? The First Aid summary is known to lie (personal experience). In order to see the hidden Container, you need to click "View" within Disk Utility and select "Show All Devices" before the hidden Container appears on the left pane of Disk Utility.
You can try clearing the NVRAM by using the following command in the Terminal app (located on the Utilities menu on the menu bar):
nvram -c
This command is safe to use on an M-series Mac (be careful of any other variations since most references are referring to an Intel Mac, but those Intel Mac options rarely work on the M-series Macs). You need to reboot the Mac after clearing the NVRAM so that the system can provide the default settings to the hardware & OS. You may see a "permission denied" for some items such as computer name & related items & perhaps some other things (depends on system configuration). I've had to use this in order to boot some Macs M-series laptops when the Display settings got into a weird state after a macOS update (was a macOS bug...actually two bugs).
Make sure to disconnect all external devices in case one of them is causing a problem.
If you are using any anti-virus apps, cleaning/optimizer apps, or third party security software, then uninstall them by following the developers' instructions since these types of apps usually cause more problems than they solve because they interfere with the normal operation of macOS at a very low level.
Also, make sure all your third party apps are also completely up to date.
