I had the exact same thing happen to me two Christmases ago. We were driving from Toronto to Halifax after the holidays (2 day drive). We stopped in Quebec city overnight and the temp was down to -30 C (about -25 F). The next morning I started the car up, and in about half a minute the oil pressure guage dropped to 0. I immediately shut the engine off (hadn't driven anywhere, just warming it up) I checked under the hood and there was a lot of oil all over the place, especially on the hood pad over the dipstick. It was those breather hoses that go to the top of each valve cover. A lot of short trips had built up a lot of condensation in the engine adn it gooed up those hoses pretty good, that combined with the freezing temperature (which solidified it) caused the oil to blow out the dip stick. It took a good 6 quarts to fill it back up (takes aty least 8 quarts at an oil change). I had the car towed to a loacl garage (MB dealer not open on Sundays). It took several hours for the car to thaw inside the garage. They took off the valve covers and they were lined with a white gunk, same with the hoses. They cleaned them all up withsome kind of cleaner they had, put everything together, filled up the oil and we were off. I had my mechanic check it after we got home (11 more hours of driving). Fortunately there was no damage done, and it hasn't caused a similar problem yet. I now check these hoses and the oil filler cap for the white gunk twice a week. As winter was coming on I noticed it starting to build up again, but two or three hour long highway runs a week seems to get the engine hot enough to clean this stuff up. That was my problem, yours might be different, but for sure get it looked at. Good Luck.
1995 E420 - retired
1986 420SEL - retired