Sima was born on 3 July 1906 in Mundra, Transylvania, Fogaras County, Kingdom of Hungary (today Mândra, Brașov County, Romania), although some sources incorrectly list his birthplace as the nearby city of Făgăraș and his birth year as 1907. Between 1926 and 1932 he studied at the Faculty of Letters and Philosophy of the University of Bucharest, serving as councillor of the National Union of Christian Students of Romania. Beginning in 1932 he began to work as a high school teacher of logic, Latin, and philosophy in Caransenbeș, later transferring to a school in Lugoj, and finally to Timișoara.