Airbag Sensor

I was driving and realized that my airbag sensor light appeared. I decided to take it into the shop to get it fixed and a couple weeks later it appeared on again. Therefore, I took it in again to get looked at. Believe it or not it came on a third time. So, I just took it in today to get it fixed again. I really hope its only a problem with the sensor light; therefore, it would be an easy problem to fix. Anyone have any thoughts about this?