Mobile Pages and Category having frequent freeze while loading

We are experiencing a problem when loading (not all) and not all of the time. Pages and categories sometimes take up to 10-15 seconds to load. It shows the page, but you cannot ‘scroll’ through the page for those 10-15 seconds. Its as if it is freezing.

Anyone any ideas?
Only on mobile and website is www.chelleon.co.uk
Mainly this product page on mobile https://www.chelleon.co.uk/avst-3-environ/