Are all heart vibrations sensation due to afib?

No: Heart "vibrations" or palpitations are due to many different heart dysrhythmias. They occur whith extra heart beats called premature atrial or ventricular contractions, or rapid heart rates including normal tachycardia or abnormal supraventricular tachycardia. Atrial fibrillation is an irregularly irregular heart rhythm. Electrocardiograms or special monitors help define the rhythm type.

No: Can be due to murmurs or other arrhythmias ...

Fortunately no: No, "heart vibrations sensation" can be due to premature beats, supra ventricular tachycardia, atrial flutter, atrial fibrillation and even non-sustained ventricular tachycardia. Sometimes palpitations are due to your own self awareness of your heart beat.