IRREGULAR HEARTBEAT. On chest sometimes.

My problem does not fade away. It gets clear automatically But again comes back suddenly. My Pulse is not Even paced I have normal ECG with Sinus arrythmia, which is Normal everyone said. ECHO is normal too 2 months have been passed. I also consulted a cardiologist in previous month. He said all is okay. Now Again I have irregular Heart beats, Fluctuations, I feel sound of pulse pounding on everywhere, palpitations happen. I hv Gas Confined in left side also. It is so uncertain. No body knows when it will happen. Even if I take proper rest or lying down HR goes up 127 around in pulse oximeter and smart watch. Sometimes goes below 60 , RHR always on 55-60 though I am not an Athelete. Then again it comes back to Normal. It is like Flare up. Some day it happens 3 times a day, Not always palpitation happens but I can feel a signal that everything is not okay No other obvious concern is there. No chest pain or breathing problem. Only Irregularity and Gas trapping on chest sometimes.