Are you using a mouse u might have hit the middle mouse wheel and that would make it scroll on it's own

Hello it sounds like you have to much stuff on your computer and the memory and storage is running low and that will make the computer run slow or u have to many things open at the same time close some of the pages u have opened and close some of the apps u maby be using to many and then uninstall some of the apps and programs u are not using and see if that helps it speed up again or u can go to settings and click on backup or reset and click on reset the computer and windows back to its factory settings and that would most likely help it to run faster I know that cause I had the same thing happened to my hp laptop and that's how I fixed it by factory reset it back to the factory settings