12 volts won’t shock you, so it has to be something else. I would think that you may be on to something with the wiper motor. If the wiper motor is on and stuck, it would pull a lot of current. When the circuit breaker opens, it breaks the current flow. When you break the current flow on an inductive circuit like a motor, the voltage rises to to try & keep the current the same. This is how your ignition system works.
I bet the timing was just right with you touching the shift lever & the breaker tripping. The voltage must have found a path to the lever.
