attempt to index global 'c' (a nil value). Why?

I wrote a script that gives the player a surrounding shield whenever they press a certain key. However, when I load the game (both in Studio and on Roblox) it says "Players.Player1.Backpack.Shield:3: attempt to index global 'c' (a nil value)

Here it is:

p = game.Players.LocalPlayer
c = p.Character
hum = c:WaitForChild('Humanoid')
pressed = false
cooldown = 3
utilitytime = 10
show = p.PlayerGui:WaitForChild('Powers').Shield
local a = hum:LoadAnimation(script.Animation)

s = Instance.new('Part')
sw = Instance.new('Weld',s)

function onKeyPress(Shield, userInputState, inputObject)
	if userInputState == Enum.UserInputState.Begin then
		if not pressed then
		pressed = true
		print('Q was pressed')
		a:Play()
		s.Parent = workspace
		s.Shape = 'Ball'
		s.Locked = false
		s.Anchored = false
		s.Transparency = 0.5
		s.CanCollide = false
		s.BrickColor = BrickColor.new('Cyan')
		s.Material = 'Neon'
		s.Size = Vector3.new(6,6.2,6)
		s.CFrame = p.Character.HumanoidRootPart.CFrame * CFrame.new(0,0,0)
		
		sw.Part0 = p.Character.HumanoidRootPart
		sw.Part1 = s
		sw.C0 = CFrame.new(0,0,0)
		sw.Parent = s
		
		show.BackgroundColor3 = Color3.new(0,0,0)
		show.Text = 'SHIELD: ON USE'
		end
	end
	wait(utilitytime) show.Text = 'SHIELD: ON USE'
	wait(.4)
	s.BrickColor = BrickColor.new('Deep orange')
	wait(.4)
	s.BrickColor = BrickColor.new('Bright orange')
	wait(.4)
	s.BrickColor = BrickColor.new('Really red')
	wait(.4)
	s:remove()
	sw:remove()
	show.Text = 'SHIELD: COOLDOWN'
	wait(cooldown)
	show.Text = 'SHIELD (Q)'
	show.BackgroundColor3 = Color3.new(0,0,0)
	pressed = false
end
game.ContextActionService:BindAction('keyPress',onKeyPress,false,Enum.KeyCode.Q)

Why's this happening? I searched online for similar problems, yet I couldn't find much help. And this script is a local script, placed in the starter pack.

The problem is that the game isn’t loading the character fast enough, therefor resulting in a nil value. To fix this problem, change it to this;

c = plr.Character or p.CharacterAdded:Wait()

Else add a wait(3) in the beginning.

Also, here is a tip; Make your variables better(don’t just use c or p, make it more clear like plr or ch)