Will forgetting to bring a translation document while driving in Australia cause problems ?

Can't rent a car.

You won't be able to get the car; without a translation document, the rental company won't give you the car.

If you can rent a car without violating traffic regulations and without being checked by the police, avoiding these three points should be fine. Car rental requires all documents to be ready before picking up the car.

You can't rent a car, even if you have a reservation. In 2016, I had a translation document when I rented a car from Hertz. I lost my documents when I picked up the car again halfway through, and they absolutely refused to let me take the car. A companion who doesn't drive but has a translation document eventually took the car in his name, and as long as you don't break the law and aren't caught by the police, it's fine to switch drivers. Now, Hertz provides blank translation documents for free, but you need to provide the original domestic driver's license to pick up the car.

Perhaps not.

You can have a translation done online specifically for a rental company.

There is a simultaneous interpretation service.