This is more common than you would guess, and the timing is not evidence that something is wrong with you.
What often happens is that the period immediately after an experience is taken up with managing it: leaving, coping, keeping the household running, not falling apart in front of people. That is a full-time occupation and it leaves no room for the rest. When circumstances finally settle, the room appears, and what was postponed arrives. People frequently describe it as coming out of nowhere. It has not; it has been waiting for a gap.
A second common trigger is something in the present that resembles the past only slightly. A tone of voice, an office layout, a piece of news. The resemblance does not have to be logical to work.
You do not have to describe what happened in order to start, and you should not feel you must. The first session can be entirely about how it is affecting you now.
This is general information in reply to a public question, not advice about your own situation, and it does not create a client relationship. If you are in immediate danger, contact emergency services.