iMac Crashes but no crash report

A bit hard to tell at this point.

What I suggest is that you temporarily remove any external devices, except the keyboard & mosue. Then start up your iMac in Safe Mode. Finally, run an EtreCheck report, and optionally, post it here if you need assistance with interpreting its results. If you are not familiar with EtreCheck, it is a diagnostics app, developed by a valued forum member, that greatly aides in troubleshooting difficult Mac issues. (There is a free version available.)

The report should provide us with some potential causes of these crashes.

Just to be sure where did you look to see if there were any crash reports? Also, did you see any messages that indicated that this was a crash vs. a kernel panic?

As mentioned, you have MacKeeper installed, this is considered malware by experienced users and should be uninstalled before anything else is done. Please locate the developers uninstall instructions and then follow to the letter. After that please restart in Safe Mode and download the evaluation version of FindAnyFile and have it search your system for anything's that says MacKeeper installed, then Trash that and empty the Trash. Then restart normally and test.

Never ever install any of the following types of third party apps:

• Antivirus
• Cleaning
• VPN
• Maintenance
• Security

They do NOTHING that Mac OS cannot already do and if anything make Mac OS slow, unstable, appear buggy and cause unwanted behaviors. In short they do the exact opposite of what most users want. Mac OS does not require or benefit in any way by installing these types of apps!!!

Doing a quick glance at the report, here are my observations / recommendations:

• A macOS does not need a "cleaner" app. You have MacKeeper installed on this Mac. These apps tend to cause more issues than resolve them. I suggest that you completely remove it and avoid using them in the future.
  • /Library/PrivilegedHelperTools/com.mackeeper.MacKeeper.MacKeeperPrivilegedHelper
• BDAqua has already mentioned about removing MEGAupdater. I second that. I see a number of posts on the Internet about it causing crashes on Macs. Here's one: https://github.com/meganz/MEGAsync/issues/726
• macOS also doesn't need an AV app. You have Norton For Mac installed. I suggest that you completely remove this app as well.

Delete this file & restart...

~/Library/LaunchAgents/mega.mac.megaupdater.plist

~ tilde indicates your home folder

Apple hid the Users' Library folders...

Method 1:

1 From the Finder, select the Go menu at top of the screen, and choose Go to Folder.

2 In the window that opens, enter ~/Library, and click Go.

Fingers crossed, do let us know please.:)

Great news my friend! :)