Most websites take a lot of time while loading their category or product listing pages. Visitors don’t bother to wait long if they don’t see any visual progress in their browsers. For this reason it’s best to display a graphic (for e.g. animated GIF) so that visitors know that the website is loading their results.
Remember any sort of communication with your visitor is better than no communication at all as you may lose a potential sale on your website.
I have coded a small example as to how it should work. You are free to change it according to your requirement.