Very jittery movement when trying to change CFrame?

I have the following code:

local LocalPlayer = game.Players.LocalPlayer

workspace:WaitForChild(LocalPlayer.Name)

local Mouse = LocalPlayer:GetMouse()
local RunService = game:GetService("RunService")
local UpperTorso = LocalPlayer.Character:WaitForChild("UpperTorso", 5)

RunService.RenderStepped:Connect(function ()    
    UpperTorso.CFrame = CFrame.new(UpperTorso.Position, Vector3.new(Mouse.Hit.Position.X, Mouse.Hit.Position.Y, Mouse.Hit.Position.Z))
end)

But when I run it, this is what is looks like.

Any Ideas?