About 3 months ago we decided Chester (our beardy) was large enough to be put on a sandy substrate, actually the fine grey 'grit' from HFF. He loved it! He was running around digging etc, never seen him happier. Then he ran under a large flat rock, hollowed himself out a 'nest' and has stayed there ever since. We've read about brumation, although most of what we read said that they usually don't do it in their first year. We've woken him up a couple of times, and he'll come out and bask, eat a bit, but by the end of the day he's back under his rock. I haven't changed the temperature of the tank, its 20-25 at night, and 30-35 during the day, and a bit hotter in the basking spot.
Any idea how long this might go on for, or what could be causing it?