Well, my little notebook plan has worked so far.
I woke up with pain in my legs -- nothing to worry about, just that pain that comes from being in one position too long -- and so I moved about, as I often do, to relieve the pain. The cats were very intelligently lying on the other side of the bed, not near my legs, as they usually were.
I immediately thought "I wonder if it's bad circulation that creates that pain?" I put it together with another experience of bad circulation and thought it might be something to write about. The other experience is actually a series of observations. I've noticed that when my fingers get cold, usually when I'm driving at night in the winter, the tips get numb. Just recently, I actually saw them and they were scarily white.
So, I put these circulation related items together and thought I could write about it. I don't know WHY, but I think that'd be asking a bit much, don't you think? ;)
Edited to Add: In response to urging to consult a doctor, I did look this issue up on WebMD. The symptoms sound exactly like Raynaud's Phenomenon. It seems to be non-life threatening, especially in the absence of other symptoms. I will mention it to the doctor, but am not planning to make a special trip. :)