STEM Restoring Employment Skills through Targeted Assistance, Re-entry, and Training Act or the STEM RESTART Act This bill establishes a new national program to support mid-career workers, including workers from underrepresented or rural populations, in reentering or transitioning to the STEM (science, technology, engineering, and mathematics) workforce by awarding grants to certain small- and medium-sized businesses to assist such workers in reentering or transitioning to the workforce at positions above entry level.