For the past few months i feel periodic vibrations over my heart which are similar, though much weaker, than the vibration setting on my phone. ?

Sometimes: this could indicate an arrythmia and at your age (84) would strongly suggest you see your Primary Care Provider and obtain a remote recording of your heart !! Do this fairly soon!!!! Hope this helps Dr Z

Not an illness: The only 2 medical conditions that could possibly be described as vibrations would be muscle twitching of the chest wall and palpitations. If the former you would see the twitching and feel it with your hand. If he latter you would be able to tell your heart was racing or skipping beats by checking your pulse. If neither of the above applies you can stop worrying about these "vibrations."