safari version 16.6.1 not responding to clicks

Sometimes Safari sometimes does not respond to mouse clicks.

It happened while posting to a Wordpress website, and on Google Docs web page. It may have happened on other sites, can't remember. It's not like the whole programme freezing. If I move the mouse the on screen cursor moves, and I can refresh the web page but that doesn't necessarily unfreeze the page. I can open a different page in a new window and that will work fine while the first one stays "frozen'.

I'm on a 2020 iMac running Big Sur, and Safari 16.6.1

Many thanks in advance for your help!