E36 headlights wont switch off

[russ328]

whenever i have been driving with the lights on, when i come to a stop and turn the light switch to off, the headlights stay on, even after the ignition is off, keys out of the car. i find that if i leave the car for 5-10 mins, then start the engine, turn the switch on, and then off the lights eventually go off.
does anyone have any idea what might be causing this problem?