You also need to make sure you don't have any macros on with KB / M, if you have G keys on your keyboard, make sure they're not activated by accident / doing stuff. You'd also want to see if it happens in a different browser. You gotta rule stuff out when things like this happen and you can't forget about bad drivers being able to affect stuff even without the hardware plugged in. Honestly I'd unplug anything USB and plug them in one at a time to see if it's one of them doing it. It also offers many other features like cropping. PicPick is a great software for capturing screenshots, which gives you a lot of options and modes for screen capturing including scrolling screenshot. Method 1: Use PicPick to take Scrolling Screenshots in Windows 10. Note: Make sure to create a restore point just in case something goes wrong. If you have a joystick or controller plugged in, unplug those because an uncalibrated joystick can do it (this usually makes characters spin in a game with no input as well). How to Take Scrolling Screenshots in Windows 10. If it's a laptop, the built in mouse in the keyboard could be it if it has one, and the touchpad could do it, even if off, if something is wrong with the driver or hardware (touchpad going out is very common), you can rule this out by uninstalling the touchpad in device manager (don't delete the driver) when you reboot it'll automatically reinstall the driver, or you can scan for hardware changes by right clicking the top item of device manager. Then, unplug your mouse and keyboard and see if it still happens to rule them out. First thing to do is reboot to make sure it's not a fluke.

Windows 10 auto scrolling