Load megamenu using AJAX

Hi, in case I have a large/many mega menu items (images etc), is there an easy way to start loading whole menu AFTER user hover/click on menu item? For now, everything load on page load, and most of users never see all the menus.
I understand there may be a delay between displaying menu on hover or click, but when there is a lot of content inside, it slow down UX and give a pretty bad score in Page Speed (as it load content that is not visible or needed).
thank you!