As I entered a single lane roundabout the car suddenly stopped very abruptly. There was no imminent danger nor were there any cars coming through the roundabout. There was no reason to apply the brakes. Fortunately there was no car behind me otherwise there certainly would have been a rear end collision. I was jarred by the abrupt stop and sustained injury to my back. I will be notifying the dealer. The vehicle has not yet been inspected. There were no warning lights or messages prior to the incident.