I've noticed that my 3 week old's chin quivers a lot like he's cold, even when he's not and his leg…

I would mention it

it's probably normal immature nervous system reaction, very common, but I recommended to mention it to your doctor next time you see him, also you can find more info in this article

http://www.childhealth-explanation.com/jitteriness.html

i've noticed similar things in my baby, her lip will quiver when she's nursing sometimes and i've seen her leg twitch before, it was wierd. i wouldn't worry too much!

Thanks ladies!

my home nurse, said it's completely normal and so did a nurse in labor and delivery! It's because their nervous system is so immature and it's developing