Jake, my spine has done that for years, and I get relief when it does. When I see my chiro, he barely lays his hands on my back and I start popping and cracking! For me it's that I am out of alignment. I have so scoliosis in my upper back so have alot of pressure on it, and I pop "out of alignment" alot.
My low back did it too, but different popping. Doc said that was scar tissue or cartilage where my injury was. It hurt before it popped, right at L4-5 I would bring my knees to chest and feel a big pressure, then it would pop, sometimes painfully, sometimes it felt good, like a release of pressure. Hope this helps. Me and my hubby walk around popping & crackin', lol