Because of the phrase 'sent the car flying' you know that this must relate to driving. We sometimes use pronouns to refer to ourselves and our vehicle, so here 'me' actually refers to 'my vehicle'. The 'something' refers to some object. It could be anything, such as a rock, a large animal, a part of a car. But probably - it would be another vehicle. And 'went' probably means 'crashed', since it 'went' with enough force to knock the car off the road. So - it means something like: "Some object crashed into the back of my car, and sent it flying off the road"