first thing you need to do is check for yourself to see if the oil is low. if not, it may be the sensor.
my yellow oil light used to turn on every once in a while for around ten seconds. the oil level was always fine, it was the sensor that was bad. if you have a bad sensor, DO NOT let it go unattended. i always told myself i was too busy and would just catch it on my next oil change. very bad idea. i recently had to replace my entire instrument cluster(approx $600) and they said it probably went bad because i let the oil sensor go for so long. this could've been bullshit but i wouldn't take the chance if i were you. i think it was an additional $180 dollars for the sensor to be replaced. definitely check it out.
<img src='http://www.bmw-forums.com/forum/uploads/post-4-1081744190.jpg' border='0' alt='user posted image' />
<span style='color:gray'><span style='font-family:Arial'>2000 323Ci alpine white</span></span>