Given that we're now into Spring it could well be a type of hay fever. (The symptoms vary. You don't always get the itchy eyes and runny nose. Sometimes you get symptoms akin to those of a chest infection).
Get it checked out with your GP or simply try some antihistamines from your pharmacist.
Try the paper bag.....scrunch top in hand & breathe in & out into the bag. It opens the lungs. For chest infections: breathe in thru nose & exhale slowly via mouth...keep hands on stomach so shoulders are relaxed.