Ciao Gabriele!
It could be a software problem and not hardware..
First of all, have done an OS update or install new hardware from when you have notice the bad behaviour of your mouse?
Bluetooth device and usb3 hardware have some problem to live together..
Try to un-coupling the mouse in the OS using the Bluetooth preference panel and coulple it again as a new device!
If this don't work, You can also would try to reset your P.Ram (shut down the computer, turn it on and before you hear the chime sound hold those 4 key: P+R+alt+cmd till your mac reboot again).