Bringing up Apple Diagnostics with keyboard shortcut

Also, the diagnostics rarely detect problems. Make sure you are holding the correct keys (Option + D) immediately after hearing the startup chime. Pressing the keys too early or too late will cause them to be ignored. And it is best to use a wired USB keyboard.

Use Apple Diagnostics to test your Mac - Apple Support

What problems or issues are you encountering with your 2017 iMac..?

The Apple Diagnostics Test will only produce codes that say: "There may be an issue with ____"

see > Apple Diagnostics reference codes - Apple Support

To get a better picture of what is actually causing a problem or issue:

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

Then port the Report, as per > How to use the Add Text Feature When Post… - Apple Community

+1 on downloading and running EtreCheck. Also, being specific rather than using terms like "I am having a lot of problems with my imac 2017. " helps us diagnose solutions rather than playing a guessing game.

By the way, do you have any of the following types of third party apps installed on the computer?

• Antivirus
• Cleaning
• Security
• Maintenance
• VPN