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 :)