Approximately once a month the car will not start. It has no power of any kind

Battery and alternator have been checked numerous times and tested good. As soon as the battery is touched with jumpers the car fires immediately. After removing cables can turn engine off and it will restart with no problem. The car will start perfectly for approximately a month then the same procedure will take place. By the way the engine is a 4cyl 1.8L. I couldn't get the engine to change in header.