Wiktionary
bundle of nerves
n. 1 (context idiomatic English) A person with an especially nervous, excitable, or fearful disposition. 2 (context idiomatic dated English) A lively, continually active person.
Usage examples of "bundle of nerves".
She remembered too well the fragile bundle of nerves she had been after Baran.
So it is no wonder that the brain, the biggest bundle of nerves, is also located there, for then orders from the brain can travel to the prehensile organs by the quickest route.
But Vaquero, though physically fit after the battle with the Dralthi, was a bundle of nerves and not really ready for duty so soon.