For freezing temperatures you need antifreeze.
You don't say how old is your car. The problem you describe can have 2 versions:
-radiator is not efficient
-water pump is not efficient.
Over the years I had to replace several radiators in older vehicles, simply because of the radiator build up, that cut the cooling efficiency.
No water wetteners, flushes and other gizmos helped.
One way to check it out is infra-red thermometer. When you stop with the engine idling at 100 C and whole radiator is close to this temperature, that means radiator is not cooling enough.
If the radiator cools drastically at the outlet, that means that water pump on the idle is not giving enough flow.

 

What I'm saying is don't use Water Wetter. It's not meant for street cars. You want to use a 50/50 mix of water and anti-freeze and look elsewhere for the answer to your cooling problem. Water Wetter is for race cars.

Anti-freeze also lubricates and prevents rust. Running 100% water is a bad idea.

 

THANKS. WHAT I WILL TRY AND DO FIRST, IS TO DRAIN OUT THE COOLANT. START AFRESH WITH 50/50 WATER & ANTIFREEZE.
THE CAR IS E420 ['97], PURCHASE LAST DECEMBER.
I JUST WANT TO BE ON THE SAFE SIDE. THE TEMP NEVER EXCEED 95.
I'M JUST AFRAID IN CASE ONE DAY, I GET STUCK IN TRAFFIC.
WHAT WILL BE THE NORMAL AVERAGE TEMP. READING?

 

Stop'n go traffic is the worst scenario for engine cooling, so any problems in this department will show in this situation.
Pressurized system with good coolant is having boiling point above 110 C, or even higher depends of the coolant mixture. If you have the situation, you might try to turn off the engine, while the electric fan suppose to run regardless ignition position.

 

Your 100 degree Celcius is equal to 212 Fahrenheit, which is the easier number for me to work with. The 212 is definitely worth watching but don't stress out about it. The key is to watch the gauge and make sure it's movements coincide with what you're doing. For example, sitting it stop and stop again traffic means the only cooling effect is provided by your puny cooling fan drawing in ambient temperature air. This is almost certainly the worst case. But, sitting in the driver's seat the high reading is logical, right? Not gonna make you a happy camper, but at least it makes sense. Moments later, when traffic clears and you are cruising at 55 mph, you should begin to see the temperature reading go down...as that ever so important forced air flows through your radiator. Your job is to watch the relative movements, not the number. Don't worry about the number until the gauge keeps rising when it shouldn't be. To know this, you have to be vigilant and needle saavy.

Dave