coolant light came on. Oil change and fluids had been completed only 2 weeksago

They completed the oil change, but I am pretty sure they will only have checked the other fluids and topped up if needed.

The level indicator will warn if even slightly low, however you need to know if they added to or checked the coolant. Most independents dont seem to keep Mercedes fluids on hand, I keep all factory fluids in my shop as I refuse to have a clients car leave and have this happen. Flip side, you'll want to make sure the level doesn't change as leaks do happen. The hope is that they maybe tested it and slightly changed the level just enough for the sensor to notice. It needs to be watched, and you need to know if it was opened or tested. Can't let coolant issues go unresolved on any vehicle, especially imports, they respond harshly to overheats.

Thanks for your answer. They just unscrewed the cap on the coolant and checked if the float was there and then put the cap back on. Do I need to drain it? Is there a particular type of coolant for Mercedes?