The smell is telltale .... monitor your coolant tank, especially when cold, such as first thing in the morning.
Look under the upper coolant hose. Often the radiator neck becomes brittle and will start as a little leak there. You can sometimes see evidence of the leak as white residue on the black plastic.
Get you head down under as they say and look around. If there are not leaks within the engine compartment, battery area, fuse box area, then explore under the dash.
It is my experience that you do not get that smell unless something is a problem.
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)