The oil level sensor is temperature dependent. It will not register any level until the oil temperature reaches the normal operating temperature. Then it will become active and let you know when the oil level is below a certain level, corresponding to half way between the low and full marks on the dipstick, or about a quart low, depending on your car's oil capacity. So, you may check the level and find it midway on the dipstick, which is technically ok, but have the light on. Which is annoying, or even alarming depending on your outlook and personality.
By the way, on my 190E 2.3-16 the oil level sensor is right at about the height of the oil level in the pan. No need to do anything serious to replace it, but it is pretty old now and always works fine. I also note when I turn to the right, mine will go off if the level is at or just below the set point.
I hope this helps explain your light behavior. Seems where you live when it is cold it takes a ride almost all the way to work to get the oil hot enough to enable the level detection warning to become active. 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)