What Causes Palpitations While Sleeping?

hi good day, i m 37 years old. i m suffering from occasional palpitation usually occured during my sleep during night, the results of my ECG goes like this Sinus rhythm with occasional ventricular premature complexes; Normal ECG i undergo 24 hour Holter test and result interpretation goes Basic rhythm is sinus with average HR of 77 BPM with minimum HR of 53 BPM and maximum HR of 124 BPM, no bundle branch blocks noted, low frequency PAC occuring singly and in couplets, Moderate Frequency PVC occuring singly and in couplets, no significant ST segments shifts, symptoms did not coincide with significant ECG changes. i m concerned about it hope you could help me..thank you.