expression
in the early period (of something); at the beginning
Used to refer to the time shortly after something started or happened. Often followed by a clause describing a state or action that occurred during that early phase.
入社した間もない頃は、右も左もわからなかった。
In the early days after joining the company, I didn't know left from right.
開店間もない頃は、お客さんが少なかった。
Shortly after the store opened, there were few customers.
間もなく is an adverb meaning 'soon' or 'before long', focusing on the near future. 間もない頃 is a noun phrase referring to the early period after a past event.
Phrase composed of 間 (ma, 'interval') + も (mo, 'even') + ない (nai, 'not exist') + 頃 (koro, 'time'). Literally 'the time when not even an interval has passed', i.e., the early stage.