the mind > emotion > excitement > nervous excitement > be in state of nervous excitement [verb (intransitive)] > become gradually (2)
intransitive. To become agitated or excited; to proceed gradually to a state of heightened emotion.
slang. to get one's panties in a bunch (also wad, knot,etc.): to become agitated or annoyed. Cf. to get one's knickers in a twist at twist, n.1 16e.