When the external temperature is in the 60's or below, and I start my car after it has been sitting overnight, the engine idles at about 1400 rpm and it takes about 3-5 minutes for it to come down to normal idle rpm. In this time, the coolant temperature reaches 50-55 degrees.

The car is an '86 300E with 72K miles on it.

What could be a possible cause for this or is this normal?

Thanks in advance.

hs