I get triggered because of my past physical abuse ALL THE TIME. This morning my daughter pulled my headphone ear plug out of my ear unexpectedly. I reacted as though I was being physically attacked - out of proportion anger, attack posture, full-on adrenaline pounding reaction. It took me a while to calm down from that one and it really upset my daughter too.
My daughter later came up to me and gave me a hug,. As she did she accidentally pulled my top back so that it was taut against my neck. I had an instant flashback of being strangled and reacted accordingly (upsetting my daughter again, although that reaction is a really common one from her hugs and I think she really should know better, although another part of me realizes she is just desperately seeking human connection with a human being who really struggles to give it).
This afternoon my cat jumped from a window ledge from the floor, in my peripheral vision. I also reacted then as though I was about to be whacked across the head.
The other day I was walking down the hallway with a colleague, and she-knows-better-but-forgot-this-time put her arm around my shoulders. I just felt the touch on the shoulder opposite from her and reacted as though I was about to be attacked from behind - I leaped away and turned in an instant with a fight pose to "face the attacker" while my colleague instantly realised her mistake and vehemently apologized.

These kinds of triggers happen every day. This is why I don't do people.