It is possible that media analysis is taking place in the background. Go to Edit>Preferences>Media Analysis and turn off all analysis to see whether that makes any difference (after a relaunch of the program). Depending on the size of your catalog and whether you have a lot of videos in your catalog, the performance can degrade significantly during analysis. The best thing is to let the program run overnight (or over many nights) to complete the analysis. If you want to try limiting the analysis, I believe that auto-creations are the biggest resource hog, so maybe just try turning that off temporarily.
I have reviewed my range of images and removed drives which are not necessary Althogh I can not remove Offline drives. I have optimised the Catalogue, re-run the thumbnail file. The Face Analysis is almost complete so I have left it operating. Currently the Thumbnail file is renewing and is expected tol be complete in the next day. I am still experiencing ‘ Not Responding ‘ messages in the Task Manager but will review this when the above operations are complete.