How old is your hen, and how long has the sneezing been going on? Have any of your other chickens had any sneezing? Can you describe your coop and it’s ventilation? Have you looked her over for evidence of lice or mites under her vent or around her neck and wings? Sneezing every few minutes can be a sign of a virus called infectious bronchitis. But usually other chickens in the coop get it fairly quickly, sneezing, with clear nasal discharge, and may slow down in laying or have wrinkled egg shells.
Mycoplasma or MG may have mild symptoms such as sneezing or lethargy, but many times it causes bubbles in one eye or pinkeye. Some sneezing may be due to poor air circulation, dust in the feed or coop, high ammonia levels, or mold from wet conditions. Here is a good link to read about most of the common respiratory diseases:
https://edis.ifas.ufl.edu/ps044