I understand that intermittent oil light problems are common on many Benz models. I'm not sure about your particular model, but on my 420SEL the oil sensor is located just below the oil filter housing near the front of the engine. I can see how going up a steep hill might cause the oil to temporarily not reach the sensor, but still be fully lubricating the engine. Also, Mercedes oil lights don't wait as long as american cars to come on. In other words the engine doesn't have to be dry to turn the light on. If this is only happening on hills, or one hill in particular, I wouldn't worry about it. Your best bet is not to rely on the guages for everything. I constantly monitor all the gauages, oil (pressure and level) temp, etc. while driving, but I also make sure I visually inspect all fluid level at least once a week, usually twice. I also make sure to look at the driveway/garage floor and parking spots when ever I backout of a parking spot to check for leaks or puddles. If you get in this habit you spot any problem in advance of serious damage.