Erased disk and re-installed Big Sur but still "computer restarts because of a problem"

Please restart in the Recovery partition by holding down Command + R on startup. Then open Disk Utility and run First Aide on your hard disk 2-4 times. If any errors appear, then this means the HD is failing and should be replaced. If the HD checks out okay, please do the following.

Please navigate to the Mac App Store or 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

Hi Holyporter,

You have a failing hard drive. Just as EtreCheck said, "Failing hard drive - This computer has a hard drive that appears to be failing" and "Low performance - EtreCheck report took an unusually long time to run."

Please, backup your files ASAP to an external hard drive using Time Machine or "copy and paste" or backup and store files in iCloud, How to back up your Mac - Official Apple Support, and then use this link, Mac Repair - Official Apple Support, to learn about service options and making an Apple Store appointment for your Mac.

Cheers,

Jack

I see some major issues, before you do anything and I mean this you need to backup the computer or you are about to lose all of your data. There is no evidence you use Time Machine to backup or anything's else to backup. Buy yourself a high quality External Hard Disk such as a OWC Mercury Elite Pro and use Time Machine to back up!!

Your hard drive is failing according to your report which means replace it ASAP. I would recommend getting yourself an external SSD such as :

https://eshop.macsales.com/item/OWC/MS8U3SSDT1.0/ & https://eshop.macsales.com/item/OWC/MOTGPWR/

Then install Mac OS on it and finally use the Time Machine backup to restore to it. This will make the computer significantly quicker and solver your failing HD problem too.

Hard drives can be tricky, sometimes they "tell" you they will be failing quickly and others it can come as a complete surprise. I have had some that last a few months and others that have lasted over 10 years. This is one of the shortcomings of HD based computer. This is another reason why many users are converting to SSD based systems as there are no moving parts to fail. While SSD can fail, IMHO the failure rate it much lower than hard disks.

In addition, the bottle neck on performance for many years has been the HD. When a SSD is used to replace a HD performance is transformed. You can find many many videos and tests online that show this. For videos look in YouTube. Below is one example:

https://www.youtube.com/watch?v=5wJ6iTav_AU

Yeah, it is unfortunate.

Did you get "AppleCare+"? If so, as long as the Mac is under 3 years, this will be covered.

Your welcome and good luck.