Typically, a herniated disc occurs when the discs in your back undergo age-related changes. As you get older, your discs aren't as flexible as they once were. Basically, your discs become more prone to a herniation.
Sometimes, you'll be able to pinpoint when you herniated a disc, such as when you lifted with your back muscles as opposed to your thigh and leg muscles. You may experience a herniated disc once you turn or twist while you're lifting. Although it's rare, a fall could cause this issue as well.