iMac restarting unwanted - need translation of etrecheck - (continued)

So with the 21.5-inch 2019 iMac, you’re dealing with a machine that (Apple) officially supports up to 32GB of 2400 MHz DDR4 SO-DIMM memory, even though you're able to physically install faster 2666 MHz modules like the ones you did.

Apple’s Intel iMacs are usually pretty forgiving with RAM speed mismatches, but these machines will clock all RAM down to 2400 MHz, regardless of what you install. That makes buying higher-speed RAM kind of pointless.

In addition the Kingston KCP426SD8/16 modules aren’t Mac-specific, even though Kingston lists them as “compatible.” Unfortunately, that generic classification means they can sometimes behave unpredictably — especially with Apple’s tighter tolerance for things like SPD (Serial Presence Detect) profiles and voltage behavior during wake/sleep cycles.

Since one already appears to have failed, I’d recommend replacing the entire set with something tested specifically for Macs. Like these:

• Crucial CT2K16G4S24AM (2x16GB DDR4-2400, Mac-specific)
• OWC 32GB Kit (OWC2400DDR4S32P)

IMHO, the OWC kits are particularly well-regarded in Mac circles because they're rigorously tested with Apple systems. Crucial is also very reliable, and they specifically flag compatibility with each exact Mac model.

First, there is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This documents describe what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community and Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support.  

There are no known viruses, i.e. self propagating, for Macs.  There are, however, adware and malware which require the user to install although unwittingly most of the time thru sneaky links, etc.   

Anti Virus developers try to group all types as viruses into their ad campaigns of fear.  They do a poor job of the detecting and isolating the adware and malware.  Since there are no viruses these apps use up a lot of system resources searching for what is non-existent and adversely affect system and app performance.

There is one app, Malwarebytes, which was developed by a long time contributor to these forums and a highly respected member of the computer security community, that is designed solely to seek out adware and known malware and remove it.  The free version is more than adequate for most users.  

Unless you're using a true VPN tunnel, such as between you and your employer's, school's or bank's servers, they provide false security from a privacy standpoint.  Read these two articles: Public VPN's are anything but private and Security Risks: The Dangers of Using Free VPNs (eccu.edu).  

Additionally, a new study ("Apple Offers Apps With Ties to Chinese Military”) is specifically about VPN apps in Apple’s App Store.

That being said and that many of the A/V apps often give false positives and interfere with optimal system performance I recommend removal of BitWarden, Little Snitch and Amphexamine. If you want to keep the Mac from sleeping just go to System ➙ Energy and turn on the option to prevent the drives from sleeping when the screen is off.

And for longer absences from the Mac and overnight shut it down. I'm from the old school and shut mine down each night. Boot time is insignificant and shutting down clears out temporary system and application cache and swap files. Keeps the system lean and mean.