I once had the exact same problem leaving my Garage which is a slight uphill followed by a slight downhill and off the kerb...... and the noise was awful.
SWMBO was in the car with me and I assumed that our combined mass was creating it's own gravity and pulling us closer to mother earth.
Since I was due to drive some distance the following day I called for fuel and decided to check the tyre pressures to be sure of good fuel economy. It was then that the cause of the scrape was brought home to me. Tyre pressures were way, way down. In my case the problem was easily solved, I blew me tyres up and voila problem solved.
I hope your problem is equally easy to solve.