I think what you're describing is more along the lines of exaggerated startle response, not necessarily triggering? When something is "triggering" in a PTSD sense, that means it is directly related to our trauma in some way. So if your PTSD was caused by a bad car accident, then riding in a car may be triggering to you. Other things that stress us out but aren't related to our trauma are considered stressors. One of my big stressors is money. It has no relation to any of my traumas, but financial issues send me spiraling. Exaggerated startle response is like what you describe. Being jumpy when we hear something unexpected, etc.
I experience what you experience, and unfortunately for me, its one of those things that gets better only when I work on healing in general. That is, there isn't much I can do to directly prevent this particular symptom. When I get startled I can use my coping skills to calm myself, but of course that's always an after the fact kind of thing. And unfortunately for me, this is one of my symptoms that has actually gotten worse as I've gone through more treatment! Go figure, right? It was bad at the beginning when I was first diagnosed, decreased a bit after I became properly medicated, increased after trauma processing (significantly) and is now on the decline again as my healing is progressing even more.
When I get startled, I do a lot of self talk, saying to myself that I am ok, I can get through this, etc. Depending on the severity, I also may need to remove myself from the environment. Small startle, ie being unexpectedly touched (in a non-malicious sort of way), then I stay in the situation and work through it. Large startle, ie fireworks, then I get myself to a safe place ASAP.