For me it was the opening title sequence. The music and the images really unnerved me.
This is my signature.

YES! I remember in more normal circumstances being asked to have a seat andto wait. Unnerving - I felt that the minute I saw those scenes - moreso in the second shot than in the first.
Another "un-nerver" was when Hamilton showed up at the first location and nobody would even look at him, making him very nervous.
Shots such as those really hit home.
I saw the best minds of my generation destroyed by madness, starving hysterical naked.