Something very similar happened to me (20, m) recently, I drank too much coffee, felt my heart racing and had an impending sense of doom being worried to the point where I was also (trying to) accept my oncoming death. This was also happening while being on an intercontinental flight which I don't recommend.

In retrospect I also have kind of similar feelings about it, although I'm afraid the experience actually caused me being worried a lot more about some minor health issues in the last year.