Welcome to Health Care Magic
You should see a cardiologist and get yourself examined and investigated...Normally, heart rate
raises with effort / with training, it slows down...The other way around as you say could be Anxiety
/ Hormones / additional nerve
paths and so on.
EKG /HOLTER (24 to 48 hour ambulatory monitoring) / ECHOcardiogram
/ TMT (Treadmill exercise ECG) / LABORATORY work-up – may all be necessary for further assessment and assistance.
The treating doctor may suggest them depending on need, based on his assessment of the situation.
Wishing speedy recovery