If it’s a hard mouse pad, it could be the mousepad is worn and too glossy for it to work well. Try it on a sheet of paper, and if it’s still doing it, it could be the laser is losing power or the battery may be getting too weak to power the laser.
The Laser bounces off the surface and goes into a receiver which is beside it, so make sure it’s clean too.
There are several manuals for tearing down the mouse too that should help.