I get this from PG mixes with certain flavors. It causes my lungs to 'clamp up'.
I changed to VG and only use that now. The problem has gone. My lungs are sensitive to certain irritants, I know this from experience - even though super high-strength tobacco cigs such as Lucky plains, Winston and so on do not cause me any problems, certain other types of irritants do (such as dust, mould spores in damp areas, etc).
Apparently there is something in PG, or PG-mix flavors more likely, that does not agree with me, which is fixed immediately by moving to VG-only. Therefore it might help you to try this out. You need to ensure that the flavors are 100% VG-based as well. I use a 100% VG mix now and it suits just fine, no more top-of-lung irritation.
This is most likely a rare thing as very few probably experience it. Those who don't are lucky as they can use any eliquid.