champing at the bit

champing at the bit (for sth/to do sth)
chomping at the bit (for sth/to do sth)
(to want to start, to be eager to begin; to be ready and anxious to do something; to show impatience while delayed, or just to be very eager to start; be tired of being held back; to be impatient or vexed, as because of delay; to be very keen to start an activity) — быть в нетерпении, с нетерпением ждать; проявлять нетерпение, сгорать от нетерпения, гореть желанием; рваться сделать что-л. или начать делать что-л.; рваться в бой; ждать не дождаться
Also chafe at the bit

..... By the time he arrived to pick us up we were champing at the bit with impatience. (CID)
..... I'm not sure if he's ready for extra responsibility yet, but he's chafing at the bit.(CID)
...... I am chafing at the bit to get started in/on my new job.
...........Though it will be hard to leave school, I am chomping at the bit to get started on my new job.
(= can't wait to get started on his new job)
...... The kids were champing at the bit to get into the swimming pool. (thefreedictionary.com)
...... The dogs were champing at the bit to begin the hunt. (thefreedictionary.com)
......The phone companies are champing at the bit to expand into these new lines of business. (CID)
...... Republican U.S. Senate candidate Thom Tillis Tuesday dismissed critics who say he’s ducking debates and said he’s “chomping at the bit” to tout his legislative record. “The difference between me and my opponents is they get up and talk about what they may do,” he said. “I get up and talk about what I’ve done. Am I ashamed of that? I’m chomping at the bit.”

......Grandaddy Prince Philip is ‘champing at the bit’ to get back to work
Restless Prince Philip is anxious to get back to his royal duties after surgery.
......The 92-year-old is “champing at the bit” to return to work, only a fortnight into his two-month convalescence after an abdominal operation. (express.co.uk)

Etymology:
bit is a metal mouthpiece used for controlling a horse, a piece of metal in its mouth that allows a rider to control its movements;
champ is to bite or chew noisily.
Refers to the tendency of some horses to chew on the bit when excited or nervous, impatient or eager.