1
If you are using a laptop with a touchpad, open the Settings App, then go to Bluetooth and Devices - Touchpad.
In there, lower the sensitivity on your touchpad, or if there is a a Palm Check setting, enable that.
2
If you are using an external mouse, connect that to another PC to test if there is a problem with the mouse.
If there is no problem indicated with the mouse, if your mouse requires specific software or drivers to be installed, reinstall those to test if that resolves the problem.
Another option is to change the surface you are using the mouse on to test if the surface is causing the problems.