Slow boot up and program opening on iMac Retina 4K

Here are some recommendations that can help solve the problem with slow loading and opening programs on iMac Retina 4K:

Check the amount of free disk space. If the drive is more than 90% full, the computer may slow down. To free up space, you can move files to another disk or external storage device, and then delete unnecessary files from the boot disk.

Close all unused applications. You can find out how much memory is used by your computer and applications using the System Monitoring application.

Update the software. As a rule, developers create and optimize their applications for the latest version of macOS.

Disable program autoloading. The more programs you open automatically when you log in, the slower your Mac starts up. To disable auto-upload, open "System Settings", go to the "General" section, then to "Login objects". Select the input objects and click on the "Minus" button to disable the automatic opening of the program.

Check the disk for errors. The speed of the Mac may decrease due to errors in the operation of the drive. You can check their availability using the Disk Utility.

If the problem persists, it is recommended to contact the service center.

EtreCheckPro is an excellent tool for looking into slowness and other problems.

Download and run the free version of EtreCheckPro, from > https://etrecheck.com/en/index.html

Then post back with your Report, as per > How to use the Add Text Feature When Post… - Apple Community

Please post the EtreCheck report that was requested. Using only Disk Utility to check the health of the drive is unreliable at best.

However before you do ANYTHING, backup the computer using Time Machine to safeguard your data. On an 8 year old computer the chances of a failing HD are very good good, so be smart and protect your data!!!!

Another upvote for posting an Etrecheck report. All we can tell from your DU screenshot is that your Apple Fusion Drive is not "split," which is good. However, DU does not tell us its speed or any health issues.

With one report, it will also help us see if software interferences are causing the slowdowns. People load up their Macs with useless fearware and wonder why their computer is slow.

Etrecheck is the development of a long-serving and trusted ASC contributor. It is a reporting app, not a "fix-it” app, expressly for displaying information in these forums. It is the only tool that lets us effectively help in a setting where we can neither see nor touch your computer.