Thank you so much, BrianK90!
Sorry for not being more "technical" when describing my (and many others) issue.
I'm in a iMac (Retina 5K, 27-inch, Late 2015)
3.2 GHz Quad-Core Intel Core i5
32 GB 1867 MHz DDR3
AMD Radeon R9 M380 2 GB
Monterey 12.6.6 (21G646)
The issue occurs on my 2 identical iMacs and the MacMini
It doesn't happen with other browsers (FF, Edge anywhere)
It does happen in some websites, not all of them. (as far I have noticed)
I cleared all history, cookies, to no avail.
In the MacMini, Safari has no extensions in addition to no history or cookies. All data was cleared, and yet it happens on it and on the other 2 Machines.
I have noticed that happens mostly, (but no exclusively) in images that change continuously, like in a slideshow or when you hover on one image to see a detail of it or a variation (like in IKEA).
