Why does the mouse move by itself?

Question

Mouse

The cursor began to move by itself, not in jerks, as when the mouse is on an uneven surface, but in circular motions across the screen and the mouse keys began to be pressed (it lasted for several seconds). Pulled the mouse out of the usb port, but it did not help. After restarting the PC, this stopped happening.

What could it possibly be?

*no touchpad, only one mouse connected