It isn't a natural sentence, use active voice when you are doing the action.
I am reading the book at the moment - I am reading it now ( it is open on my bed or I have it in my bag, I have started reading it though 'at the moment' does not have to mean: this second, because this second you are reading this post and not the book) .
I am going to read the book - in the future.
The car is going to be repaired - somene will work on it in the future
The car is being repaired - someone has started working on it.
Generally for everyday speech choose active voice, passive voice is formal and not that common. It isn't natural in your example and it sounds strange even in the example with the car. It would be good in the news on TV: A strange object has been found in the dessert. The experts suspect it is UFO. It is being examined by a team of specialists at the moment. It is going to be sent to NASA.