It can't be too bad for the motor - the front wiper is already intermittent.

Our rear wiper motor is the same as most have been for decades. To start a wipe, you complete the ground side of the circuit. After the wipe starts, a contact within the motor completes the ground side of the circuit until the wiper reaches its home position again. The internal contact then opens.

All any delay circuit needs to do is to ground the motor lead for about a half-second to start the process. The simple circuit I am building grounds the wire for 0.5 seconds and then opens it for 9.5 seconds. The motor does the rest.