Hiding/sleeping

Anybody have any thoughts on why my baby boy would suddenly be hiding/ sleeping in his cave?
We're currently camping. (His first time ) we got here Thursday about 4:00 pm. He was fine most the night and most the day Friday. He ate dinner Thursday and breakfast Friday morning. He had a good poop Friday late morning. He was good up until about 3:00 then he went in his cave. Took him out at 5:00 for dinner, then he went back in immediately after. Turned his lights on at 7:00 am this morning (Saturday), at 9:30 am he still hadn't come out. I took him out and tried to feed him but he wasn't interested. He stayed out for a couple hours, then went back in. He is in right now. About to take him out to get some sun because it has warmed up. He is in a smaller tank (20 gallon) just for camping as it's easier for transport. He is parasite free, just had a test done and got results yesterday. All in all he seems healthy. Just trying to understand why he might be doing this. I guess it could just be the change, just wanna get other opinions.

Sunday evening and aside from taking him out to get some sun he's been in his cave and still not eaten much at all. Any thoughts would be great

It is most likely the change. He is used to being in a certain room with the same view and smells and the new environment might seem theatening. You may find he is still out of character when he gets home for a few days.