Are you used old version? There was an issue with gamepad connected to pc.
I always use the newest version of the demo that comes out, how ever, the problem is still there for what ever reason. Even in the update before this one didn´t fix it. The update that came out now, I still have to play. Then I can say more.How ever even if I unplug the controller from the PC the character still moves to the left on its own.