Mercedes Benz repair: Frequent stopping, radiator fluid, ml 430

Question
1999 Mercede-Benz ML 430 with 99256 miles, New York City. I was driving my Fathers SUV for the last week as he borrowed my car and Initially it stopped when I was driving on the Highway and I had to pull over. When the car cooled down to 70 degrees Celsius the car started again and was able to drive for a few more miles till the temperature goes above 80 degrees celsius and then i wait for it to cool down again and then it starts. This has happened for the last week so now i am afraid to take my fathers car out and I don't know what the problem is, I saw the radiator fluid was a little low so i filled it up but i have not had the courage to drive the car again. Can you help me with this problem by telling me what is the issue?  

Answer
Answer:
This must go to the MB dealer before it fails for the last time.
There are several possible issues, however, I would need the scan codes, and may need it to fail with scanner connected.

Please read this thread first.
98 ML320 No Start - No Fuel
http://www.mercedesshop.com/shopforum/showthread.php?t=96360