iMac crashes irregularly when no apps running.

If that fan control tool is being used to slow the fans, that’s an immediate suspect.

SSD is a suspect, and DriveDx info would be interesting. TRIM disabled on that add-on 1.00 TB SSD isn’t going to help performance. That SSD will be running at “erase” speeds; slow.

Given the crashes and the MDS Spotlight errors and the lack of TRIM and the rest, the SSD is the best potential culprit. A test for that eould be an external SSD macOS install, and boot and run from that, and see how stable the iMac then is.

Diagnostics might find something:

… Use Apple Diagnostics to test your Mac - Apple Support

But Diagnostics aren’t great at finding transient errors.

If any sketchy or cracked apps are loaded (given that security is disabled), all bets are off.

Depend on the age and config of your iMac, it is highly likely that the HDD is failing and constantly disconnects itself if your system has a hdd or Fusion Drive.

If this is the case, you can try out DriveDX for a more human friendly diagnostics.

And, if it is the HDD that causes problems, you can either replace it (need to open up the iMac and relatively not easy to do for models newer than 2011), or disable the HDD using terminal commands. If the disk was set as a Fusion Drive, you can use terminal to separate the SDD and HDD first.

You can also use USB or TB external Hdd/Ssd as a boot disk or data storage to compensate for the loss of the old HDD. External USB-C SSDs are considered best options to work with many iMacs that tend to have internal HDD failures.

Hmmm, wonder why it says it's off but installed recently?

Just noticed...

2023-07-08 13:54:15 mds_stores Crash (6 times)

MDS is Spotlight.

Long shot...

Open Terminal and run each of these one at a time

/System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/LaunchServices.framework/Versions/A/Support/lsregister -kill -r -domain local -domain system -domain user

sudo /System/Library/Frameworks/CoreServices.framework/Frameworks/LaunchServices.framework/Support/lsregister -kill -seed -lint -r -f -v -dump -domain local -domain system -domain user -domain network

killall Dock

sudo mdutil -E /

sudo mdutil -i on /

Rebuilding a drive index can take a long time, so be prepared to wait whether you do it through the System Preference panel or the command line.

I can't tell much at all from that.

We need to see what all is running & machine specs, a report from this will not display any personal info...

EtreCheck is a FREE simple little diagnostic tool to display the important details of your system configuration and allow you to copy that information to the Clipboard. It is meant to be used with Apple Support Communities to help people help you with your Mac. It will not display any personal info.

https://www.etrecheck.com/

Pastebin is a good place to paste the whole report if you capture the URL while there…

Workable but harder for me to work with...the Note tool on the bottom of this editor's toolbar, as shown in the image, to copy and paste the output from EtreCheck. In a Reply before you click post, look for this to add longer texts...

If you're forcing sleep, set a sleep delay time you can live with and let it sleep on its own.

My experience in putting a Mac to sleep is it's not the best way to do it. I get delays coming out of sleep and for reasons I can't really put a finger on it's just not the optimum choice.

Can't say for certain, but looks a bit like...

Security updates disabled

May be involved.