Usually this happens due to the acid content in the stomach...it gets turning when they know they are going to be fed...
Now it can be from the acid hitting the esophageal irritation from hairballs. So you can try using an over the counter hairball medicine first thing in the morning and at night for a few days and see if there is a difference.
Another option...first thing is to give 1 tsp of Maalox and feed about 45 minutes later.
Let me know how it goes.
Dr.V
Dr. D.A. Vamvakias
Veterinarian