I’ve optimized my website with WPRocket, SG Optimizer, Asset Cleanup Pro and Cloudflare CDN (siteground). Everything is loading perfectly but when the website is loaded for the first time there is a half a second where everything is broken but then it fixes itself. I learned that its a flash of unstyled content. You can see my site below.
Usually, this happens when CSS is loaded in the footer of the website. On your site, it’s loading in the header, which should prevent any flash of unstyled content.