Adjectives

(s)nervouseasily agitated“a nervous addict”, “a nervous thoroughbred”
(s)anxious, nervous, queasy, uneasy, unquietcausing or fraught with or showing anxiety“spent an anxious night waiting for the test results”, “cast anxious glances behind her”, “those nervous moments before takeoff”, “an unquiet mind”
(a)nervous, neuralof or relating to the nervous system“nervous disease”, “neural disorder”
(s)aflutter, nervousexcited in anticipation
(s)skittish, flighty, spooky, nervousunpredictably excitable (especially of horses)