not a doctor...ok...but an instructor / examiner over many years and having seen many different reactions...
i was just wondering if you have the heater on too high...and then it struck me...i wonder it could have anything to to with hypoxia..( which i doubt at such a low altitude ...and i presume there are no other symptoms like those normally associated with that )...
and then i wondered if there could be any traces of carbon monoxide getting into the cabin...and once again this would not normally be a symptom i would associate with that either...
on the thought advanced by gingernut...is it possible that this is just something as simple as excitement...if you were to do a few flights maintaining not above 1000/2000...what would you experience..?? i assume you have tried this and so i have to consider that it has something to so with altitude or the length of time you are spending in the aircraft since if you are talking about over 6000 feet i have to assume these are long trips...( taking me back to the earlier two thoughts )..
what would happen if :-
1) either you do as lon a trip down lower...or
2) you try a short trip above 6000..??
..in other words..how long does it take to manifest..??
the dean