If your Xbox One Wireless Controller has a malfunctioning thumbstick and you cannot properly navigate around your Xbox One, see the Xbox One Wireless Controller Has Malfunctioning Thumbsticks problem page for possible problems and solutions.
Every controller stick has what's called a "dead zone" and that's the area that the controller’s position is registered as 0 or no movement.
Over time and with use, the stick’s idle position will drift out of the dead zone, an indicator of this is if it seems loose and moves easily, and will seem to move position on its own because the hardware detects the stick is out of the dead zone.
There are all kinds of novel solutions, like supergluing elastic bands to the inside to counter the drift and hitting them straight down with a hammer... I don't recommend it.
Unfortunately, the only real solution is to replace the stick and its board-level hardware, you'll need a soldering iron.
Fortunately, they're quite cheap I couldn't recommend this particular product because I've never bought one myself, and I reckon you could shop around and get a bargain somewhere.