Hi there,
it looks like your Cache plugin is deferring the loading of scripts, including the script that is used for the masonry display, which is causing the layout shift of all the elements below your posts.
If you open the site in Chrome, Right > Click Inspect, go to the Network tab and change Online to Slow 3G, keep the dev tools open and refresh the site. You will see the header and footer is loaded then the deferred masonry posts is loaded after.