Hi all,
As a few others have mentioned already, addons would be a major cause for issues like this, so as a first step please make sure you disable any addons while troubleshooting this.
Other than that some of the reports here don’t really have a lot of details about what the problem is precisely, though the most common mouse issues and solutions can be found here:
Spinning Camera While Moving Mouse in World of Warcraft
Mouse Clicking in Wrong Location
Mouse Pointer Invisible
Mouse jumping/centering FIX
A lot of the steps will be overlapping between different problem descriptions, but hopefully this should cover a solution for the majority of cases!