nervous

easily agitated; "a nervous addict"; "a nervous thoroughbred"

causing 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"

of or relating to the nervous system; "nervous disease"; "neural disorder"

excited in anticipation

unpredictably excitable (especially of horses)