Hi!
This phenomenon is called the flash of unstyled content, and is usually caused by lazy loading of the CSS files.
In your case, the cause is, that the conditional CSS loader is enabled, and another plugin/code (probably cache plugin?) is removing a piece of inline CSS code from the header, that would prevent the flashing effect, until the CSS is asynchronously loaded. To resolve it, you have 2 options:
1. Turning off the conditional CSS loader option
2. ..or making sure that this priority CSS is within the site header as inline CSS to prevent the flash of unstyled content effect:
[html].asp-try{visibility:hidden;}.wpdreams_asp_sc{display: none; max-height: 0; overflow: hidden;}[/html]
These should do the trick.