How to make FPS camera movement?

I have this zombie game where I want people to walk around in First Person Lock but I wan the camera to bob up and down. I also have the walkspeed set to 8 if it has any effect. I tried this...

--This Part is Fake... OBVIOUSLY--
while true do
    if game.Players.LocalPlayer.Moving = true then
        game.StarterPlayer.StarterCharacter:GetChildren().Position = ypos+5
        wait(0.3)
        game.StarterPlayer.StarterCharacter:GetChildren().Position = ypos-5




--Thats just an  IDEA of what I want it to do so don't just report me because that is fake ok?--

Anyways does anyone know how I could implement this?

I also know about Humanoid.Running but Idk much about it.