_DirtyJetsamMemoryLimit

If you are running 10.13 as your profile shows, try running the combo update. It installs all previous updates plus the new one, which can replace any files that may have become corrupted. If that doesn't work, do a backup, preferable 2 separate ones on 2 drives. Boot to the Recovery Volume (command - R on a restart). Run Disk Utility and select First Aid. Then re-install the OS.

OS X Recovery

OS X Recovery (2)

Download macOS High Sierra 10.13.4 Combo Update - Apple Support

Sorry about the formatting, I'm on the iPad. Here is my EtreCheck blurb. Are you really on an iMac Pro? I've only seen one EtreCheck report from someone with an iMac Pro and that person was reporting something similar. EtreCheck showed that the machine was restarting due to overheating. I was skeptical about shoving that kind of server hardware into an iMac form factor. I wonder if you are having the same problem.

I wrote a little diagnostic program to help show what might be causing these problems. Download EtreCheck from https://www.etrecheck.com, run it, and paste the results here. EtreCheck is perfectly safe to run, does not ask for your password to install, and is signed with my Apple Developer ID.

Disclaimer: Although EtreCheck is free to download and use at first, it will eventually ask you to buy a license. There are also other links on my site that could give me some form of compensation, financial or otherwise.

Hello ernstfromhaarlem,

Your freezes are likely being caused by something else. That message is normal and occurs thousands of times a day on millions of Macs per day. I strongly suggest avoiding looking at logs in Console.app. There is nothing you can learn there.

All I get from the Mac Support is, to reinstall my Mac. (not an option for me)

No other option, sorry.