iMac stuck on home screen

They can cause many issues on a Mac including possibly yours.

No Anti-Virus software or so-called “cleaning” apps are needed or recommended for Mac OS. They can conflict with Mac's own built-in security. At best they will slow your Mac by using unnecessary resources and at worst will bork your entire system. Your Mac has all the built-in protection you need.

macOS - Security - Apple

Try booting up in Safe Mode:

https://support.apple.com/en-us/HT201262

Good news, that's to be expected in Safe Mode. Go to System Preferences > Users & Groups > Login Items and use the (-) button to delete all the Login items. You can always add them back with the (+) button. Then restart normally and see how it works.

Do you have any antivirus or cleaning apps installed on the computer?