I had my first one at about 40.
Long before I new I had anxiety though I may have had it without knowing.
I find flickering lights will sometimes bring it on.
Other times they seem to just happen for no reason?
My GP told me to take 2 Paracetamol when it starts but I've found that they go away in about 20 mins with or without it.
The most annoying thing is when I get one while driving.
Flickering sunlight off other cars or through roadside trees used to set it off so I always wear polarised sunnies while driving now.