I do know what you're talking about - you explained it very well. I tend to think that my "startle response" is heightened just before, or during a flare. It's a signal for me to check my stress/activity level/other signs, etc. so I can hopefully calm things down and avoid any progression to flare or worsening of one already started.
Don't know if that helps - I hope you're not heading into a flare!