Phantom files

Whilst learning how to do an advanced spotlight search I was horrified to find dozens, probably hundreds of copies of files in the various formats I use. I searched on this very valuable site and the only answer I could find was to relaunch my finder. I have done so, but the problem seems to continue in fact they seem almost to be regenerating themselves as I watch! I'm not a new user by any means. I can't find a rational explanation for this behaviour which doesn't cause me a great problem as I have plenty of disc space (at the moment!) but it is making searching for a legitimate file extremely difficult. I'm using the latest Big Sur OS on a 2019 Mac. I've done the usual stuff with Malwarebytes and Etrecheck - neither of which reported a problem. Can anyone help me please. Am I missing something obvious?