This phenomenon is called the flash of unstyled content, and is caused by lazy loading of the CSS files. You have some sort of minify plugin active that aggreagates the CSS files and loads them on the bottom of the page, outside the header – causing the flash effect. I highly recommend turning off this feature, unless you are very experienced with CSS, and can add the critical CSS rules to the header to prevent the FOUC effect.
Alternatively you can try this custom CSS, add it to the critical custom CSS section, so that it is loaded in the header:
This will set the search height to 0, until the main css is loaded, which will change it back to ‘auto’, with the correct styling. In this case make sure to clear all layers of cache, and also make sure that this CSS is indeed within the header as inline css.
Best, Ernest Marcinko If you like my products, don't forget to rate them on codecanyon :)