1 - Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.
2 - Safe Mode will also eliminate Third Party Software, extensions and drives from loading
3 - Does the issue present in this mode ?
4 - Sometimes a Safe Boot followed by a Normal Boot will just put things right.
5 - If not - there could be something in the main User Account playing up. To further isolate this - Set up users, guests, and groups on Mac. Then log out of the Main User account and log into the dummy account and test again if the issue persists.
6 - If the issue is present in the dummy account - then, this appears to be a System Wide issue on the computer.
7 - Download the Application Etrecheck directly from the Developer.
The application is free or paid from added features.
It will take a Snap Shot - both the hardware and software.
The Report will Not Reveal Any Personal Information.
Post back the Full Report - copy and paste - >>>> using the Additional Text Icon ( 3rd Icon to last ) <<<<
We can have a look at the report for possible issues and may have possible suggestions to resolve the issues.