How to stop making the character follow the camera in First Person?

Basically I was making a game which is supposed to be in first person, the game allows you to pick up certain parts and use them (just like tools). I also added a feature where the head moves where the camera is but then realised that it would be hard to make the head move along the y axis (because you are in first person). I wanted the player to be able to move their head around but when they move it too far the character rotates, so I need to stop the character from automatically locking the its y axis to the camera's y axis. This doesn't have to be possible but I want the game to look a bit smoother in general. Thanks.