Why we are not comfortable at an ambiat temperature equal to our body temperature?

Answer 1

It all has to do with the transfer of heat energy. Our body creates energy by being alive. It feels/operates badly if it overheats--like any machine. It needs to radiate heat in order to not overheat. Energy flows from greater concentration to lesser concentration. So, if the ambient energy is less than our body's energy it radiates into the surrounding atmosphere. If the surrounding atmosphere is greater, the body absorbs energy getting more or overheating. It tries to compensate through use of evaporation by sweating, but sometimes this isn't enough--if there's more moisture in the air. ("It's not the heat it's the humidity.") The energy must be moved away from the body. So, even if you simply sit in front of a fan moving air away from your body, the energy can radiate into the air moving away and the body can dissipate that energy. Odds are you will never be in a system that cannot allow for some energy radiation from the body completely.
It all comes down to the flow of heat energy.

Answer 2

For the same reason you get warm under a blanket :) Heat doesn't freely move in and out of our bodies - our skin exists to trap warmth and keep it there (we are hot-blooded animals, unlike fish). That means any heat we generate doesn't leave our bodies instantly. So if our body is cold, the heat warms us up. If the temperature outside is equal to our ideal body temp, then all the generated heat will increase our body temp and mechanisms will then work to expel that heat.

Heat is generated as a result of reactions in our bodies. Think of it as a useful by-product.

Answer 3

Our CORE temperature is 37 degrees celcius. Our SURFACE temperature is much less. When our skin is exposed to 37 degree weather, it feels hot, since there's quite a difference.

Answer 4

We are generating heat that we need to get rid of. If the air temperature is high we need to sweat to get rid of this heat.