Air Bag Light On problems of the 1999 Lincoln Town Car

My air bag light blinks on and off for about 90 seconds then goes off for about another 90 seconds then comes on and stays on I was told by the mechanic at the Lincoln dealership that I do not have any air bags when the light is on the problem? not known until I spend $$$ finding out why then spending more $$$ to fix it.

Vehicle is equipped with driver and passenger frontal and side airbags, the airbag light comes on indicating a problem with the system which wont protect the occupant in event of a crash or it will deploy unexpectedly, resulting in a crash. Dealer cannot determine the caus eof the problem. Please provide further information.