electrical gremlin

[Budfreak]

i was sitting at a traffic light this morning and i had my headlights on and my vent fan on med. when i suddenly heard the fan die down and when i looked up everything was real dim and the car was idling rough and my air bag light flickered on just a little bit for a second. everything was fine again when i got moving but when i got home and stopped the idle wouldn't drop below 1000 till i shut it off and restarted it and it idled at 600 like always and i couldn't get the problem to happen again no matter what i tried. something smelt hot when i popped the hood too. any help guys?