Painless vibration. Is absolutely fine.

Respected Doctor, I am experiencing with the below symptoms. With the below symptoms route me to the right direction of treatment - I feel a kind of slight painless vibration sometimes in my chest area, exactly at the centre - Considering it to be palpitation, it usually starts during 2nd half of the day - This occurs at irregular intervals - In order to rectify this, coughing usually stops the palpitation momentarily - If I sleep for 10 to 12 hrs a day for next 2 to 3 days, there is no such behaviour seen at all for next few days - I have been expriencing this since last 18 months - To rule out any heart disease, I have undergone heart checkup tests last month - ECG, Echo, TMT, Lipid profile and few other blood tests. Local Cardiologist told confirmed that heart is absolutely fine. Thank you, Regards, Jayant