SketchUp stalling, beach ball spinning

I have a iMac running OS 10.14.6 Mojave, 4.2 GHz Intel Core i7 and 48 GB of ram
running SketchUp Pro Version 21.1.331
and every few minutes I am watching the beach ball spin
Activity monitor tells me SketchUp is using 3.43 GB

Whats going on?

Perhaps Autosave is running? How large is your SketchUp file? When is the last time you purged unused stuff from it?

Do you have a 3d connection device, there was a time when they caused memory runaway.

Thank you for the feed back
I now know the problem is within the model, I have purged unused but it still persists
need to do a little more house cleaning