In reply to illepo:
Does your office feature that blight called "Air Conditioning?"
I always used to scoff at the idea that air-con makes one sick -- particularly when I lived in Cape Town, where the Summers are really hot. Since I have moved to Germany, however, where the hot-bits in Summer are comparable, I have been living and working in buildings that don't have it and I haven't had so much as a sniffle in 26 months. Extrapolating from this single data-point leads me to conclude that there is some correlation, here.
I used to experience what you describe and, today, I wonder if it wasn't precipitated by the change from the natural outside world to the stale and artificially cooled office climate, where the air has been exhaled multiple times between the wider sky and your lungs, is too dry, and probably was fanned directly down the back of your neck by a ceiling mounted vent above your chair at some point in time.