Why does my car stall out in a parking lot @ idle when warm!

What is your question?

car will be warm 3-4 mile drive to store I park, shop, than pull out and it stalls out! ONLY at low idle speed. Also I can always smell coolant when the car comes home in the garage, but NO LEAKS. Does it need a change & Flush. I just bought the car it has 72,000 miles. ALSO FLUSH TRANSMISSION & Change filter or NOT ??? Thank You,