sounds to me like a relay problem, sounds like its sticking,  if you have a
manual it should give you an idea where the relay is, I'm sure some here
will be able to tell you . They should be pretty much standard so not
expensive to replace.

Gary

According to the diagram in the Haynes manual, the relay for the rear wiper
motor is attached to the motor.
Take the panel off the tailgate and have a look. There should be red and
yellow connectors to the motor. The red one has two wires, A221 is a
permanent feed from fuse 4 (or possibly 22), and 523 is the switched feed
from the control stalk.
Does the wiper work when you operate the washer? If so then you have a
supply problem on one of the two wires on the red connector. If it does not
work with the washer then there may be a problem with the motor itself.
First check that you have 12 volts on A221 (this will only be wen the
ignition is on, or at least in the accessory position). Then check that you
are getting 112 volts on wire 523 when the switch is operated.
If you are not getting volts on one or other of those wires, check where
they cross from the body to the hatch, as that is a weak point, and wires
often break in the little rubber tube.