2010 Malibu won't crank

Our 2010 Malibu didn't turn over despite the battery being charged and no previous problems. Mechanic tested and stewed awhile, then disconnected the battery leads and held them together for a minute. Reconnecting the leads the car started right up, mechanic explaining something about capacitors needing to drain, and this problem might not happen again. Less than a week later it did. The same solution worked. Anyone with a clue about what's going on?