If it is related to the heart it could be insignificant heart spasms. For some insight: A coronary artery spasm is a brief, temporary tightening (contraction) of the muscles in the artery wall. This can narrow and briefly decrease or even prevent blood flow to part of the heart muscle. (myocardium). If the spasm lasts long enough, it can lead to chest pain (angina) and possibly a heart attack (myocardial infarction). These spasms may also be referred to as Prinzmetal angina or variant angina. Unlike typical angina, which usually occurs with exertion, coronary artery spasms often occur at rest. You may want to rule out some irregularity with casrdiovascular system as it could be serious.