How would you do a idle animation, if you have a weapon out?

I know how you play an animation:

local animation = Instance.new("Animation")
2	animation.AnimationId = "http://www.roblox.com/Asset?ID=144884906" -- ID here
3	 
4	local animTrack = Humanoid:LoadAnimation(animation)
5	animTrack:Play()

But how would I do it if this animation occured when your character isn't moving and will continue to occur providing they are not moving, (Maybe a:)

while true do 

Or something like that.