I think it would be best for you to find a level spot and, after the car is warmed up, check the oil using the dipstick. Pull it out, wipe it off with a clean cloth or paper towel, then insert it again and pull it back out to read the level. Once you read the level, note the mileage and then, assuming the level is between the two marks on the dipstick, go ahead and drive. When the light stays on, read the oil level again, note the mileage and either fill it with another quart, or change the oil again.
Keep track of the mileage when you refill and when you check the oil level, and when you change the oil. This will help you get a handle on your rate of oil consumption. If the level falls below the minimum mark, you should add oil to bring it above the minimum level. Most of my cars take nearly two quarts to go from the minimum level to the full mark. When you get the light and the level readings coordinated and quantified in your mind you can respond to the warning lamp as you feel is appropriate.
Sometimes the manual calls for a number of liters to fill the engine, and we have quarts, so you end up shorting the engine fill slightly. This leads to a quicker oil level warning unless you make up the difference.
I did not mean to suggest you should ignore the warning lamp. I am sorry if I confused you, I was trying to note it does not indicate the oil level is below the safe level, since it is yellow. It indicates you should check the oil level to find out where it is as the level has dropped from a known safe level. The oil level check is supposed to be done as noted in the earlier post by bobbyv. Once you have gone through this a few times you will have calibrated the light to the dipstick level and be in a position to wait to respond if that is what is called for, or add oil at the first flicker of the lamp, if that is appropriate based on your car. Good luck, Jim
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)