With MBD, my little beardie had an acute form of it when it was still in its early stage. His legs and head were "shivering" for a few seconds due to the lack of UVA/
UVB light. I see that beardies tend to have their own symptoms. And yes they can hide their symptoms but sometimes you gotta look real closely for these tiny symptoms.
If you suspect that your Beardie has MBD, try to arrange your tank in a way that your UVB/UVA light is close to the basking light where they are most likely be. And put some kind of place where he can climb up closer to the light like a branch or something. Mesh tends to block out some of hos needed rays so I have mine directly in his tank (once you arrange it, itll look messy but its a good temporary when you get something bigger for him when he grows up) ofc, Idk what you are using. I use a Reptisun 10.0 hood and a seperate basking light.
Also make sure you are dusting his vegetables and insects with multivitamen and Calcium with D3.
It does not hurt to take him outside into the direct sunlight for an hour a day. What I do when I am unable to take him outside is to open the window, let the sunlight stream in and comfortably put him on a towel in the sunlight.
I just suspect MBD because of his weakness in his limbs. My local reptile shop person described MBD along the lines of "trying to walk after excersizing too much. Their bones are not well developed".
Above is just a routine i do everyday to prevent MBD even though he has lost all symptoms and is doing really well. I would really advise you visit your local vet since he seems very weak. Prolonged MBD can result in permanent damage to your little guy and extra calcium supplements might be needed.