I Have An Occasional Fluttering/spasm Just Under Mu Sternum. No

I have an occasional fluttering/spasm just under mu sternum. No pain, just a nuisance. I thought it might be too much Advil that I was taking for a toothache but I have been off the Advil for a few weeks and it has come back after being gone for a while. I don't seem to be having any digestive issues. I am a 63-year-old male in good health.