Okay this is something I've seen rarely but it's there and without any other symptom of illness or discomfort I see at very rare times head of my tiel moving while she's asleep! Her beak and head normally is into feathers of her back and the movement I am talking about looks like she wanna fit in her head in the plumage, like adjusting her position to go deep into those feathers of her back! Head moves like saying a "no" buried into back! Because it is a little like shivering so that worries me sometimes! I'll try to post a video but anyone here ever saw something like this?