I was driving a long roadtrip from Texas to California, split into a couple segments over several days. At one point, my adrenaline and heart rate suddenly spiked. I felt freaked out but could not see a reason for it. I checked all my mirrors, traffic was busy but seemed to be moving along normally. A few moments later my vehicle was rocked by a semi-truck blowing past, traveling much faster than surrounding traffic, and missing my vehicle by what seemed like an inch.
The roadway was curved slightly, so I think the semi was in a blind spot when I was actively searching for the problem.
It's interesting that a subconscious process could alert me to a problem, in this case it didn't help me resolve it, but at least I was alert and looking. It had never happened before so there was a bit of confusion as well (why am I suddenly freaking out?) - but now I know how to pay attention if that feeling happens again.