A quest worthy of the most wizened adventurers!

I come to you but a humble snake keeper, with little experience of dragons and lizards. Near to myself is an ensnared bearded dragon, a few years of age, in a 4x2x2 cave, split up from it's mate late last year after brutal mating attempts. Nothing has changed in terms of his environment however he is hardly moving around anymore so any wisdom would be massively appreciated.

If husbandry is correct and your Dragon is otherwise healthy... probably brumation.

See below: https://www.beardeddragon.org/articles/brumation/

Thanks I'll definitely look into this, not actually my dragon I only keep snakes it's just for a friend after he expressed concern to me.

When was the last time he had a soak, and what type of UVB are you using?