Welcome to HCM,
You are suffering from palpitations that is rhythm disturbance of heart there are many causes for it there could be ectopic beats known as extrasystole or there could be irregular heart beats.
Your rhythm becomes normal when you exercise that means when heart rate is increased then it becomes regular.
You should consult a Cardiologist
who can analyse it in ECG and if required a stress test
or holter monitoring may be done to know exact abnormality.
Once it is diagnosed it can be treated you should avoid too much tea or coffee and use of tobacco or smoking and alcohol.
You are also having cervical radiculopathy
due to compression of nerve it should be treated by orthopedic surgeon and Neurologist
This is commonly treated by using low pillow, analgesic,muscle relaxants and Physiotherapy
Hope this helps.
Dr. Akhilesh Dubey M.D.