What do you mean with auto-scroll ? Is this about a website loading more content if you scroll down the page or do you mean the auto-scroll feature like you get if you middle-click on a webpage and get the auto-scroll icon or something different ?

• Settings -> General: Browsing: "Use autoscrolling"

Do you mean on Facebook, it works normally for a while but then starts runaway loading of new content? The developers are trying to sort it out. Some users mentioned it could be related to low memory or their browser cache being very full, but it's not very practical to monitor those issues in advance.