Got it, thanks for explanation.
So when the server side is taking a while to return data the page will look blank/frozen as you mentioned.
There are a couple of options.
The easiest if you don't want to code much is to make another page, the pre-loader.
Send everyone to the first page (pre-loader) which has a nice loading screen, then on load auto redirect to the form page.
This should keep the loading page showing until the page loads.
( though there are exceptions I will below )
If the page is still blank, then it's loading via a script.
So you can add a popup loading screen before that script starts, then remove it when it's complete.
Those are some ideas how to get it down.
Shopify Development: jcbellc.com