In reply to nikoid:
I have the same, together with a blocked nose during the night. After lots of trial and error, it appears to be my pillow or, more precisely, dust mites in the pillow. Who knew you are supposed to wash pillows, and at 60 degrees or more to kill the little f***ers, if you want to reduce the effect. A lot of pillows can’t be washed or must be washed at low temps, so may be worth having a look at changing the ones you’ve got?
Then again, could be something completely different!