Tap the F9 key on your keyboard once and see if that helps: you may have turned on SNAP, explained in Help in LT if you don't know what that is.
Clean your mouse, especially if it's the older roller-ball type (or roller-ball trackball): and clean the roller guides too, build-up can also exhibit such behavior.
Replace the mouse and/or uninstall the mouse driver and let Windows run it to see if the problem goes away. ◦