Shimon was born in 1929 in the city of Sinwan in Yemen. His parents made aliyah with him in 1936. His father Yosef was a silversmith, while his mother Devora was a homemaker with six children. Shimon studied in Talmud Torah. At age fourteen, he joined the Palmach, but a year after that he moved on to Lehi, which was fighting the foreign occupier. In Lehi he was known as Eshet and then Gilead, and he had many varied roles. At first, he disseminated promotional materials. Soon, he was taking courses in light arms and was responsible for a group of fighters. He participated in many attacks on British Army bases, including Kfar Syrkin Airfield, as well as the Barclays Bank robbery and the attack on Haifa Railway Workshops in 1946. In the last of these, he was injured while jumping from a retreating vehicle. He was captured by the British and court-martialed along with seventeen of his comrades. At the trial, the fighters defied the authority of the British to judge them; they declared themselves to be prisoners of war and demanded their rights as such. The fighters were sentenced to death, but this was commuted to life imprisonment.
A few months before the British left, Shimon fled from Atlit in a suitcase, with the assistance of a detainee who was being released.
Shimon enlisted in the IDF along with his fellow Lehi members, serving in Battalion 89, the commando unit of the 8th Brigade, under the command of Moshe Dayan. He participated in all its battles in the south and the Negev, and was discharged in 1949 as an IDF disabled person.
In 1956, he married Ziona and they had four children: Smadar, Noa, Binyamin and Shanit, as well as numerous grandchildren.
He spent forty years as a bank teller. He retired in 1994, in Tel Aviv.