My iMac keeps shutting down and restarting after installation of MACOS Big Sur version 11.3 update

Hi Trebor44,

I believe we need to proceed with an EtreCheck report. EtreCheck is a useful app to diagnose and identify issues, both hardware and software. It is trusted by many users. Please follow the steps outlined below:

1. Navigate to: https://etrecheck.com and get the free version of EtreCheckPro.
2. Download it. It is a free and trusted app. It is often recommended here on Apple Support Communities. 
3. Open EtreCheck, and before running the report, be sure to check “Allow full Drive Access” at the bottom of the EtreCheckPro window.
4. Run the report, and put it in a post, as seen here: https://discussions.apple.com/docs/DOC-250000211. We will then examine the report for issues in your Mac.

Cheers,

Jack

Please do the following:

Please navigate to www.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.

When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed to get your system running well again.

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click https://discussions.apple.com/docs/DOC-250000211

LeRebel,

Please create your own thread. While you have similar symptoms what may be causing them are likely totally different than the OP's. I know you want your issue fixed, however posting a "me too" is called thread jacking and is considered rude which I am sure is not your intent. What I would recommend the you do, is to create your own thread and post an EtreCheck report of your system and post it. Then someone can take a look and see if there is anything in the report that has red flags. Failing that, I'd suggest taking your computer to your local Apple Authorized Service Provider to have it professionally diagnosed in the event it is a hardware issue. Below are instruction for the report:

Please navigate to www.Etrecheck.com and download the free version of EtreCheck. Once you have you downloaded the app and installed it, please run the report and save it. This report will help us get a good idea what has been installed on your system and help us be able to diagnose what may be wrong.

When you have your report, you can attach it when you reply to this message and we can then review it and help you determine what is needed to get your system running well again. 

For instructions on how to download your EtreCheck report and attach it to your reply to this message please click https://discussions.apple.com/docs/DOC-250000211

I also have the same problem of my iMac 2017 randomly restarting. Talked with two online support staff at different times. Brought it to the local Apple Store to run diagnostics. Only conflict was between the two apple RAM and my two upgraded RAM which had worked well for 3 years. We elected to remove the apple RAM as it was smaller. Still the same problem :(

Running out of solutions. Can't use this computer now since I don't know when it will restart. Really frustrated as this is my main work computer. :( :( :(

It appears you may have some hardware failure. Locate an Apple Store near you for evaluation and repair: Get Support.

Cheers,

Jack

My apologies. Was not my intention to hijack or behave rudely.

I know and no reason to apologize, I was just trying to show you how others on these forums like to communicate.

I had to shutdown my iMac by the button and start it again. Then it stopped rebooting.

Just noticed this thread is for the Big Sur 11.3. I had the same problem with 11.4 just now. And resolved it with hard reboot as described above.