I Have Intermittent Pain In The Center Left Chest Area

I have intermittent pain in the center left chest area - always in the same place. It started a couple of days ago and I thought it was just a gas bubble or something. It seems more painful when I inhale deeply. Frequency is 5 to 8 times an hour, approximately. I am 71 years old and have generally excellent health. the pain isn't really sharp and doesn't last more than a second. It doesn't seem to matter if I am sitting or walking.