Re: Character walks forward by itself

Check your dead zone settings.
My Newest PS4 Pro controller had stick drift right out the box, had to raise the dead zone setting for the left stick to get my solider/tank from auto moving.

As above, and if you're using an Elite V1 or V2 controller there's a tool in the accessories app where you can check stick drift (might work with regular controllers too. Haven't checked). 

I would still recommend trying a different controller though. Being a new controller unfortunately doesn't guarantee it'll be fault free. There are reports of the Elite V2 controllers having drift straight out of the box for example. It'd mean you could rule this out at the very least.