Could be a poor electrical connection, as previously suggested, particularly a poor earth. I don't know Micra's well enough to say there are known fault areas but many vehicles have them.
To test for this you could lift the wiper blade off the screen and then switch it on: this reduces the drag that the motor has to overcome, thus reducing the current drawn and therefore any voltage dropped across bad connections. If it works now then it does point to a poor connection somewhere. This will of course not fix the problem but help as a part of a diagnosis.