Increased frequency of hairball vomition can correlate with the seasons: Length of daylight and changes in duration of daylight cause hormonal changes, and fur growth/shedding will increase. Spring and fall signal these changes.
There are many over the counter remedies for hairball problems that frequently will solve a minor problem. Long-haired cats suffer more than the shorter varieties. Frequent brushing will reduce the amount of hair ingested whilst grooming.
Obviously, other gastrointestinal problems can cause vomiting. However I am assuming that you only find the actual hair cylinder/plug and nothing else.
If the over the counter remedy does not work, then see your veterinarian.
Dr. Van Lienden
Dr. Raymond Van Lienden DVM
The Animal Clinic of Clifton
12702 Chapel Road, Clifton
Virginia, U.S.A. 20124