Hello,
Welcome to ehealthforum and thanks for writing
Pain in the neck area could generally be divided into muscular problems and spine issues.Problems in the neck muscles could be related to a sprained muscle, which often results from sudden movements, incorrect postures, etc.In the spine could be related to problems in the bones of the spine which are called vertebra, most commonly arthritis.spondylitis etc.
The possibility of a sudden jerk due to work out can be a possibility in your case.According to the description it does not seem to be due to angina as it usually presents with heart pain which may be radiated to shoulder or arm.Along with that other symptoms as dizziness,sweats,palpitation,fatigue might be present.
Relax yourself as the previous tests were normal and you have been following a proper lifestyle also.If at any point of time the pain arises again or there is development of any unusual symptom then consider visiting a Physician for evaluation.
Take care!