I agree with baron. I am a firefighter/paramedic and have been doing the job for 12 years. The symptoms you describe go along with a few things but with physical exertion you could be getting overheated. Your body compensates by going into shock to protect its vital systems which is the reason that you feel so cold. There are however a number of things that can cause this.
Overheated
Panic/Anxiety Attack (Do you have tingling in your fingers or toes?)
Anemia
Dehydration <--- Causes the most issues when exerting yourself, do your lips chap a lot? WATER not gatorade or other drinks
Underlying heart condition <--- Unsustained ventricular tachycardia --- you have a rapid rate for 30secs give or take then back to normal...a-fib very common condition that many people live a normal life with
Electrolyte imbalance <-- bananas do the body good
Do you have or ever had seizures? The hyper awareness makes me think this is possible....and no a seizure isn't always like what is seen on tv where people are flopping around...yes that happens but most are unnoticed.
I could keep going for a while. Anyway is the doc you are seeing a PCP or a Cardiologist? If not a cardiologist, consider seeing one instead of regular doc. Hope this helps and I hope that you get this all figured out.