Menus dropped down when page launches

Hello,
I may not be able to find the answer because I may not be asking the right question so if this has already been asked and answered I am sorry for that.

I have an issue when my site first loads. The menus are all dropped down and expanded for a few seconds and then the page appears correctly. I am not sure what to do to fix it or in fact, even where to look.

The site is https://www.thepcmr.com and this is happening on iPad chrome, iPad Safari, Chrome, Edge and Firefox on PC so I am sure it is something up with my site settings and not just the browser.

Thank you for your help
MinkiSan

The page I need help with: [log in to see the link]