Flashbacks can be very uncomfortable and difficult to deal with. I also know what you mean by random, seemingly dumb triggers. From what I've learned, once a neuropathway is well-established, it seems our minds will find any means they can to go "down that road" again.
I have found it helpful to try and think as little as possible when it is happening to me. I will focus on an inanimate object in front of me and try to look at nothing else. Then, I remember something that an EMT did for me right before I was diagnosed.
Flashbacks for me trigger panic attacks when they get bad enough. The worst panic attack I ever had was triggered by a movie that had nothing to do with my trauma. I was staying at my best friend's apartment for a few nights before moving in to the dorms for my first semester of college. My memory of what happened that night is very fragmented. (No substance abuse or alcohol, I was just that absorbed in my terror.) She tried everything she could to distract me, but for whatever reason, everything she said just seemed to set me off even worse. It got to the point where she didn't know what else to do, so she called an ambulance.
I remember being on the porch, and someone in a blue uniform who I assume was an EMT sat down next to me and told me if I didn't calm down he was going to have to give me a tranquilizer and that would mean a ride in the ambulance and a sleepover at the hospital. I remember begging him not to do that and to please just help me. Then, he did something that still helps me to this day when it gets to be too much for me to handle. He told me when to breathe.
"Inhale. Exhale."
For whatever reason, those two simple words and the action associated with them helps me be mindful of the one thing I feel I can't control when I flashback and panic (my breathing) and helps me control it - I breathe in only when I say "inhale"; I breathe out only after saying "exhale".
It doesn't have to be out loud. You can say it in your head. I've actually told my girlfriend about this and how it helps me because sometimes even I'm too far gone to do it for myself (or I just say it really fast since I'm worked up so it doesn't help at all, lol), so she does it. It helps.
I thought I was weird for doing this, but then they did it during guided meditation when I was in group treatment. So it is a technique that may work for you.
Whatever solution you find,
Maliginity, I hope it's a healthy one.
