Sometimes I let my bearded dragon fall asleep on me outside of his viv but he skin darkens and gets stress marks on his stomach. He doesn't puff his beard out or get annoyed with me when I wake him up to put him back in his viv, but it makes me worry about his health. When I put him back in his viv to warm up he goes back to his bright colors and loses the stress marks. I'm assuming it's because he's cold while he's asleep on me but does that mean it's not safe?