Need help: InDesign very very slow with spinning beachball

Having a world of trouble running InDesign. It's impossible for me to work sometimes. I get the spinning beachball almost constantly. This happens when I:

• Switch to InDesign from another app
Once I actually get ID to open:
• Click any palette to open or close it
• Switch between open ID docs
• Click on objects or text
• Copy and paste from other apps or within ID
• Select a tool
• Change a color

Virtually anything I try to do.

I just upgraded to a new iMac because I thought the age of my old one was the problem. Apparently not. It was brutally slow on the old iMac, taking 30 seconds or more to do any of the above. On the new iMac, that's down tp maybe 15 seconds, but still incredible frustrating.

I followed some online ideas but nothing seems to make any difference.

One thing I tried to do was to trash IDs preferences but of a few methods I tried, I couldn't find the pref files / folders referred to.

There are several posts here of people with the same problem. The potential solutions offered have not helped me so far.

Any additional help with this will be greatly appreciated.