Looks like you are using sand , and really hope it's not calcisand or vitasand or gravel.
Please remove the particulate substrate AS A MATTER OF HIGHEST PRIORITY , particulate substrates are very dangerous to bearded dragons who are prone to ingesting the particles which clump together in the gut and form blockages and impactions. The stuff is lethal to bearded dragons.
It's not worth the risk to your dragon's health and life to have particulate substrates of any kind.
Your new little spikey child will be a lot happier and safer on paper toweling or tiles.
He is too young to brumate. Does he do this a lot? Does he spend time out basking too? This would be concerning if it was his main behavior but if it just happens now and then and he is otherwise active, eating well etc then it's probably OK.