As we are talking about a video file and not an animated GIF file, you will have to manually duplicate the movie intro a video editor. You can use Windows Movie Maker as it's built in the operating system by default.
The procedure is very simple: start Windows Movie Maker and add your file to the timeline for as many seconds you want it to loop (for example add it 20 times to have a 1 minute loop file) then export it based on your preference and upload it to YouTube if you want to share it online.