You could check if there are any specific webparts that could contain any scripts.
?Contents=1 (http://example.com?contents=1 or http://example.com/sites/example?contents=1) to the end of your site url to see all the webpart that exists on the page that has the problem. If you find any Content Editor Web Part or Script Editor Web Part, those could contain the scripts that slows down the page load.
Edit the site if you find any of the webparts mentioned above. If this problem only exists for a single site then it should not be scripts added to the masterpage.
Or you could use the F12 developer tools to see if you can find anything.