I've experienced the symptoms of Reynaud's Syndrome for the past couple of years. I'm not sure what brought it on for me but I do know that I have to be careful not to get even a little bit cold because I can suddenly feel extremely cold, even on a warm day. The main symptoms for me are the white/numb hands although if it gets really bad, I can feel cold all over.

I don't know why there's a delayed onset of symptoms after a ride. I think maybe your core temperature stays up for awhile after exercise so maybe that's why. I find that even on the warmest days, I need to change out of my sweaty clothes immediately following a ride. It seems like adding wet clothing to the body's natural cooling mechanism is a big trigger for me.

I've found that, at a minimum, I need to keep my core warm. Depending on how cold it is outside (or in the room), I may need to work on keeping my extremities warm too. An example of this is that I have a hard time wearing sandals in air-conditioned buildings in the summer. My feet start going white/numb!