Hertzler was born in Savannah, Georgia. His parents were from Port Royal, Pennsylvania, and his family is descended from German-speaking Amish families. His father John G. Hertzler served in the U.S. Air Force, and his mother Eleanor Frances Beaver Hertzler was a Latin and French Teacher. His family lived in cities around the world including: St. Joe, Missouri; El Paso, Texas; and Casablanca in Morocco. He grew up mostly in the Washington, D.C. area, and attended Bucknell University, playing linebacker on their football squad. While there, he got into acting when the drama department recruited him for a production of Marat/Sade as they were looking for a big guy for one of the roles. After graduating in political science in 1972, he got his master's in set design at the University of Maryland, and attended law school for a year at American University. While he was in the DC area, he worked in the federal government, including with the Nixon Administration for the National Environmental Policy Act, and took an assortment of jobs to practice theatre including a waiter at a dinner theater, a bartender, and a cab driver.