for example, are there any JavaScript functions that are called repeatedly throughout the page? or are there any CSS styles that seem to be overriding others? maybe there are some images or videos that are being loaded dynamically somewhere in the code. once you start to get a handle on what's going on, you might be able to see how it all fits together and figure out where things go wrong
but honestly, without more context, it's hard to say for sure what's going on here