MAC software (Named OSX) is incredibly reliable and secure, but relies on underlying hardware to work right. MOST but not all issues trace back to hardware on a MAC.
But the built in diagnostics are not very good..
STORAGE DEVICE
Partial Failures. Older: HDD (Hard Disk Drives) and newer SSDs (Solid State Drives) can be diagnosed with DriveDX at this link. it’s a small download and is easy to install. The Trial Version runs 14 days, enough to figure out if you have any problem NOW.
No need to install the “Monitor” phase if it asks during install.
Anything but a green [OK] result is cause for some concern especially if a RED warning comes up- a BIG concern! But read on about Temperatures.
AMBER can have mixed messages-
Google the specific issue mentioned.
This is NOT something “Disk Utilities” can fix.
But if you get a Green, no reason not to run that now.
Note that there is no reason NOT to be using “Time Machine” for MAC BACKUPS. Generally this is a USB device which is NOT easily detected with DriveDX but could be to blame- Errors in external storage devices can slow down the MAC resulting in “BeachBall Of Death” spinning wheels. Check how recent your latest backup is?
Unplug the device to see if the Slowdowns cease.
Try and launch a backup now.
Warnings that Time MAchine cannot write to the drive or that it doe snot even show up are a clue. Unplug it for now.
Buy a spare 1TB USB device from Amazon & use that first- Reason is, in some circumstances, the backups may be readable but not writeable- Reformatting it and re backing up is a Plan, but would leave you with nothing for a while, especially if it refuses to format, hich is a real test of mechanical problems.
TEMPERTURES
the average MAC has several temperature sensors on the various hardware: CPU (Important!) battery, hard drive etc.
Nothing should approach 70c/160f
If it DOES there is likely dust in the vents or failing/failed fans.
This will bog down your MAC as it throttles back its CPU and GPU to prevent damage
Blow dust out with compressed air or a cleaner can of air.
This utility checks fan speeds AND temperatures:
https://www.crystalidea.com/macs-fan-control
If it does not help-
your cooling fans may be blocked, jammed or otherwise failed.
recycled Parts are available on eBay, etc.
BATTERY
This utility is the Best, and it’s Free.
https://www.coconut-flavour.com/coconutbattery/
it shows you now only the CHARGE level of your battery- which is what you see on the menu bar anyway- but more importantly its capacity to HOLD charge, which decreases with age.
100% when new, after a few years when this drops below 80%.
So it won’t run so long off its cable- But can result in current surges causing reboots, etc.
So also look at the other info on the screen to tell you current consumption and charge level. As a side-effect: It can show you battery condition of attached devices like iPads, iPhones, etc.
Not all softwares will work on all versions, especially on older equipment. Search at the site for previous editions that might work.
So first consider that your MAC is backed up reliably somehow.
Check For Mac OS Updates.
A failed Hard Drive (HDD) can be upgraded to SSD
500GB is about $70, and 1TB is about $100 on amazon
OTHER ISSUES
Motherboard Woes, Video Chip Issues and moisture, etc can wreck havoc with your sanity. the Apple Store may or may not be helpful with more detailed diagnostics. On more modern MACs you can hold down the “D” key during startup to run internal Diagnostics.
To Be Continued
Your comments are welcomed