Don't know for sure about you because I don't know you. I can tell you that in my case it was because of my age and the form of the religion I still practice today. Mostly, the changes that came with that age.
At least you recognize that it is for no good reason. That puts you way ahead. A trip to the doctor is not a bad idea. There are options for dealing with these feelings that you can discuss with the doc. If that does not work, there are actually skilled and trained people in schools, also clergy, and help lines.
Keep in mind that if a given solution is not for you, that does not mean there is no solution. Keep at it until you find what works. Good luck.
Well, it could be a swing in hormones. Give it a day or so and see if it passes. Keep a calendar of these times, and see if there is a pattern.
Sometimes it's a chemical imbalance in your brain. If so there's not really a cause, but anything could trigger it.