Most probably because you pressed the crouch button (ctrl). The thing is, this doesn't make you go lower, I need to get a player model with animations first. For now crouching only increases accuracy, decreases recoil (how much depends on the weapon) and stops you from walking. The crouch upwards recoil for G36 variable I set to 0. A bit unrealistic, but I did it to show that you can set these variables are flexible and can vary from weapon to weapon.