Do you mean the airbag light (red, picture of a stickman wearing a seatbelt with an airbag in front)?
If so, it is usually the wiring harness under the drivers seat, or some junk that has become wedged under there and is affecting the weight sensor. That's where I'd start.
If the seat moves bag and forth a lot, over the years, the wires can start to break and cause intermittent airbag warnings.
If everything under the seat looks fine you'll have to start pulling codes to see where the problem is. I think the key dance and most at home scanners will not pull airbag lights.