1998 BMW 525i estate 80,000 miles

The car displayed the airbag and seatbelt warning light which then slowly dimmed out, the next day when I turned the ignition on the radio, clock, wash-wipe, cruise control and horn would not work? Turned ignition off then on and everything worked ok, however, whilst driving car the interior light came on dim then went off? This fault has reoccured several times, if I turn the ignition off then on the above fault goes away? The airbag and seatbelt light has never come on since, however, when I sometimes turn the ignition on the radio, clock. Wash-wipe, cruise control and horn seem to not be powered from the vehicle? Is there a 'common' relay or control module that powers the above item's which may not be activating everytime?