Sorry if I'm stating the obvious but what your describing sounds like ataxia - which is a wobblyness or difficulty with balance and unfortunately there can be a lot of causes, but it does sound a bit odd so it could be weakness. I would assume the most common cause of ataxia would be metabolic diseases and trauma but there are many other causes like an infection of the central nervous system, vestibular disease, medication toxicity, other toxicity - of course there are more than this, so I still think a vet is your best bet.
In this case I wouldnt expect it to be a metabolic disease like calcium deficiency or even hypoglycaemia because his body condition is good and those 2 diseases usually have a slow onset - particularly if they are receiving some supplementation. I assume that he's not on any medication at the moment since he's normally healthy
Could he have come into contact with any insectides or other toxins recently?
Have you tested the pain response in his forelimbs? that's the best way to tell if they've lost feeling or not
He doesn't have a head tilt does he?
Edit: sorry on re-reading that it sounds like he doesnt seem to be aware of where he is placing his feet?, in mammals it can be assessed by placing the animals foot so that it is actually standing on the top surface, the animal should quickly flip it back so that the bottom of its paws are on the ground. I'm not sure if its assessed the same way in reptiles.
I must admit that I don't have any experience with ataxia in dragons so I am speaking from a general point of view of what I do know about it, hopefully someone whose experienced it in dragons or has picked up on something I might have missed can chime in soon.
