weird activities

97 740i with weird electric issues. There seems to be a motor running under the dash near the center console; sounds like a fan when then igniton is off. Also a hum in the left speaker while the ignition is off and and when the ignition is on and the stereo on, the hum goes away until the headlights are turned on. Also, when the stereo is turned up loud, the seats, mirrors and steering reposition themselves automatically. Any one with similar problems, please help........