Anyone know why my gerbil is sleeping out in the open?

Lately these last few weeks I’ve caught him a few times sleeping out in the open instead of in his burrow. He has over 6 inches of bedding in his cage so he definitely has enough of it. And his cage isn’t dirty or anything I keep up with it and I just cleaned it yesterday. I’m worried this could be a sign of stress or he’s close to dying. Besides him sleeping like he’s been acting normal.