Why does my kingsnake burrow so much?

I have a banded CA kingsnake. I got it 2 days ago. It has been burrowing a lot since I got it. I have fed it 2 pinky mice. I thought that it was nocturnal because it came out a lot more during the first night that I had it. But it is night now and it is still burrowed under the bark bedding. I know that it is still in the terrarium because I have 3 locks on the lid and the snake is not big enough to push off the lid even if I had no locks on it. Why is it burrowing and staying under the bedding so much?