automatic headlight problem

i own a 99 chrysler lhs and i have left the headlights switch set to automatic since i bought it. just recently i noticed that the headlights would flicker off and on with the key in the ignition but the car is not turned on. the headlights would come on then the fog lights.also while driving i hear a clicking noise and the signal light and headlight would come on then go off. i was behind a truck on a sunny day when i noticed this was going on too. any ideas of what this may be?