Fig.: to be so anxious or nervous, waiting for something to happen, that you cannot keep still or keep your attention on one thing. To be antsy

Mother has been like a cat on a hot tin roof all night, waiting for her young daughter to come home

La madre è stata sui carboni ardenti tutta la notte in attesa che la giovane figlia rientrasse

“You look nervous. Are you on edge waiting for the exam results?" “I'd say more like on hot coals”

”Ti vedo nervosa. Sei sulle spine aspettando i risultati dell'esame?” “Più sui carboni ardenti, direi”

The whole family was acting like a cat on a hot tin roof, pacing up and down the corridor, as they waited for the surgeon to come out of the operation room bringing room about the surgery

Tutta la famiglia era sui carboni ardenti e andava su e giù per il corridoio mentre aspettava che il chirurgo uscisse dalla sala operatoria con notizie sull'intervento

The factory is threatening to close and all the workers are on hot coals wandering what the future will hold for them

La fabbrica minaccia di chiudere e tutti i lavoratori sono sui carboni ardenti perché non sanno quale futuro li aspetta

Try and image a cat on a hot surface, being the roof or hot bricks: the cat would jump all over trying to get off that surface.
This idiom is the American equivalent of the British-English phrase “Like a cat on hot bricks”. The earliest use of the American version appears in the June 6th, 1921, issue of the Daily Gazette-Times. Tennessee Williams made it famous in his 1955 play of the same name, with several allusions to it throughout the play. (Source: theidioms.com)