I had this problem awhile back and did a post on here after doing some research....it's caused by changes in conductivity inside the button switches/steering wheel electronics. This can be caused by age, temperature changes, debris or cleaner getting inside them. "Sticky Button Issues" also contribute to the problem. (you also want to make sure no wires are pinched anywhere on the switches and inside the steering wheel.) You can take apart the switches and inner electronics of the steering wheel and clean the button switch contacts, connectors and other electronics and there's a conductive grease you can put on the contacts to help keep the conductivity consistent. This is definitely after you confirm its not caused by anything but the steering wheel itself(clock spring, any other bad connections, ecu, etc). Similar type issue also caused my airbag light to come on intermittently and this is usually caused by a bad clock spring, but in my case it was a bad connection in one of the connectors in the steering wheel column throwing off the required airbag resistance/setting off my airbag light. The connection just had to be clean and I checked to make sure no wires were loose or pinched. Bad/dirty connectors under the seats, on seatbelt tensioners, crash sensors in pilars and curtain airbags can also make you airbag light come on...the key is trying to find it and not spend a bunch of $$$ replacing all sorts of things before you do.