A few years ago, I was speaking to a colleague and Naturopath on the telephone while he was at his office on the weekend. It was only an hour, but he was continually clearing his throat.
This same kind of cough which is really more of a clucking of the throat or a clearing of the throat, sometimes called a frog in the throat is a result of mold spores in the air, most likely coming from the ventilation system. It is probably a reflex by the body to prevent the spores from entering the lungs.
On the weekends most office buildings shut off the ventilation system to save money. The concentration of mold spores in the air then increases significantly to be felt due to lack of forced air flow. This shut-off of the ventilation may also stop the source of the mold in the ventilation system from being vented outside the building as happens during the week.
Since mold spores in the air are not visible to humans, there is also the possibility of mold spore exposure during weekdays. In this case the cough or clucking or clearing may be more difficult to correlate with the mold spores in the air, because it is not as frequent. Mold spores in the air do not necessarily have an odor.
Mold spore exposure may not necessarily show up as an allergy to mold in standard allergy testing.
However chronic mold spore exposure can cause ill health far beyond just being allergic to mold. Therefore a serious determination of whether to continue working at your work place is warranted.