This is probably very rare, I search and found nothing related to this issue. Basically it started happening at the end of my last cycle a year ago, now it started happening from the beginning of my current cycle.
Basically, it happens only on days I train arms, particularly my upper-forearm Brachioradialis muscles, and only if I am was cycle, so it doesn't happen off-cycle.
It happens after training throughout the day and relives the next day, basically if I was to close my elbow, even without flexing the muscles, my brachioradialis muscle would bulge and get stuck, no pain, it seems as if it automatically over-flexed, or it was tense, and I would have relax that arm and use my other hand to push back the flexed arm forward, there's a twitch of pain at that point but nothing major.
It's certainly an effect of steroids, but not sure I heard of anything such as this before.