Electrical issue?

Hi, so a few months back my car would not start after taking it to the garage they told me the wires underneath the car were lime-scaled and needed cleaning etc, ever since then the air bag light would appear on the dash when I left the car running for more than a minute. The only way to turn it off is to restart the engine. Last week the car refused to start and when I did get it going it was displaying ABS airbag traction and hill stop light all on dash. Also, when I start the car I can smell a slight burning smell. Any ideas before I take it to a garage?