I have an '04 A4. When the wipers are off or in a resting position they ar on the windshield pointing from the bottom of the windshield to the top. Where they would normally be halfway through a normal wipe cycle. The wipers still work just in reverse. When turned on the wipe down to the normal off position on the bottome edge of the windshield and then return to being up on the windshield. They went to this position while I was driving and had just turned the wipers on momentarily a few times. What is wrong with them? Any idea or do I need to take it to a mechanic?