Anybody else encounter this? This is the third time this season I've experienced it; seems to be in cold winds.

• Weather conditions: high 20s / low 30s F; winds about 15-20 (I guess).
• Me conditions: jeans. long-sleeved cotton t-shirt. flannel-lined windproof jacket. wool or synthetic skullcap. windproof gloves. cotton socks and casual leather shoes. earbuds. lightly-loaded messenger bag. a little out of shape (but much better than this time last year).
• Bike conditions: upright 700c hybrid (Trek 7000). rack. one side pannier.

Hasn't proven dangerous, but has been disconcerting. I don't have any medical issues that would readily explain it, so I wonder if it has anything to do with exertion + cold winds.