early morning dry heaving

My wife (age 59) had bouts of dry heaving in the mornings when she awakes. She may go for weeks doing this, then have no problems for awhile, then it will start over again. She has a hyiedal(sorry) hernia that only bothers her at times. These symptoms seem not to be related with that, It makes no difference whether she eats or not. She had her gallbladder checked and an upper G.I. done, with negative results. She has had several polyps and a very small bit of diverticulitis. The doctors have only prescribed meds(antacids) when she has heartburn. She is on blood-pressure medication and takes a fluid pill. Does anyone have a theory as to why this may be occuring or have you had a similar experience? Also, recently she was diagnosed with a vitamin D defenciency. Could this cause dry heaving? Doctors seem to think that she is OK and have no real explanation for the early morning dry heaves. She is fine the remainder of the day. Thanks.