Hi rumpled
In my case, the limited mobility is because of a strong weakness on the legs, arms, shoulders, etc. I noticed that before the worsening of this weakness I feel something that I could describe as "a change in the temperature inside my bones", I don't know if I would describe it as cold or as hot... (This feeling, although very strange, is one of my best signs that will have an exacerbation in the MG symptoms.)