I drive a 2005 Mercedes CLK (I know, it’s old before someone tells me! Haha) and a few days ago “Coolant Check Level” popped up on the dashboard. So I topped it up with coolant only the message still hasn’t disappeared. Yesterday the message “add a litre of oil” popped up too so I added oil. Today the oil message hasn’t appeared but the coolant one is still there.
So my question is really, what do I do from here? Any advice fully appreciated!
Kindest
~a car noob
also check the level again when the vehicle engine is cold. you may have a leak and it can be low again.
Have the cooling system checked for leaks, visually verify the coolant level adjust if necessary, disregard the message, have the level sensor checked/replaced at your convenience.
thankyou for the responses everyone! will take them all on board! 
It’s also possible the electrical connection to the sensor is corroded. Ask your shop to remove the cable connection there for a visual check. It’s possible just disconnecting & re-connecting could fix it too.
You think 2005 is an old car? … lol … my newest is early 90’s. 
