This is likely happen when your site is not well optimized with resources like images , js or any script from other apps . Our app is heavily optimized for fast loading . However if the app seems to load slow you are suggested to diagnose your site from here :

If auto install is performed then the app snippet is added at the bottom of your main template. If your site has lots of heavy elements like images or videos and not optimized well then app may load slowly. The remedy is manually install the app described here . Also in order to hide add to cart button before app script loaded need to add a class name to your cart button .