Why does this momentum script lag so much when you hit max momentum?

Ok so i'm making a movement system and I started first by adding momentum. But when you reach max momentum it starts lagging pretty severely.

Here's the code (It's in StarterCharacterScripts and is a local script)

local Plr = game.Players.LocalPlayer
local Char = Plr.Character
local Humanoid = Char:FindFirstChild("Humanoid")
local Sprinting = false
local UIS = game:GetService("UserInputService")
local RunKey = Enum.KeyCode.LeftShift
local Momentum = 0
local MaxMomentum = 1
local DefaultSpeed = 16

UIS.InputBegan:Connect(function(input,gpe)
    if gpe then return end

    if input.KeyCode == RunKey then
        Sprinting = true

        task.spawn(function()
            while Sprinting do
                task.wait()
                if Momentum >= MaxMomentum then
                    Momentum = MaxMomentum
                else
                    task.wait(0.5)
                    Momentum += 0.1
                end
            end
        end)

    end

end)

UIS.InputEnded:Connect(function(input,gpe)
    if gpe then return end

    if input.KeyCode == RunKey then
        Sprinting = false
        Momentum = 0
    end

end)


while wait() do

    if Sprinting then
        Humanoid.WalkSpeed = (DefaultSpeed*(Momentum+1))
    else
        Humanoid.WalkSpeed = DefaultSpeed
    end

end

If you can help that would be greatly appreciated :)