I have a 2 year old bearded dragon which I took on from a friend who no longer wanted her. Just recently she has started tilting her head to the left and walking in circles. She can hold her head straight but most of the time it is leaning towards the left. She is still eating veg and live insects and she is still alert and doesn't seem lethargic in any way. I've just seen herself lean too far over to the left and completely flip over. I tried to pick her up while supporting her but she shook her head frantically as if she wanted to be put down. I've got her booked in at the vets but the earliest app is in 2 days!
It sounds like she has MBD (Metabolic Bone Disease) which is a deficiency of calcium and imbalance of phosphorus. Do you coat her insects in calcium? What sort of UV light do you use? If they don't have the proper UV light, they cannot absorb vit D3 or calcium. The neurological symptoms can be corrected when they have proper UV and calcium.
It's great that you have an appointment with the vet. Unfortunately, most veterinarians don't have a lot of specific experience with bearded dragons. My father is a vet and I grew up with reptiles and I still had a lot to learn when I started with Beardies.
What I would do in the mean time, is to get her outside in the sun. You can hold her on your chest and sit in the sun for half an hour or so, the UV is SO good for them. Even if it is colder outside, the sunlight is helpful.
Beardies are great pets and pretty easy to care for, the big thing is the calcium and the UV light. Since beardies are native to Australia, sometimes good information on their care is difficult to obtain. Most pet stores sell UV bulbs that are not right for bearded dragons, even when they are labeled "bearded dragon". The UV light you need is a ReptiSun 10.0. It is a tube bulb and it fits in a fixture that looks like an aquarium hood. You can find them online.
They need to be replaced every 6-12mo.
It's wonderful that you care so much for your dragon. There is a wonderful resource of information at beardeddragon.org and I will happily answer any further questions you might have. Good luck to you and your dragon.