What can be the reason of a painful tailbone with no obvious injuries?

Just happens: Multiple minor not recalled injury. A sedentary job on a hard surfaced chair or bleachers, & all of a sudden u have trouble, & once u start 2 have trouble it s hard 2 get rid of it. Even sitting on what seems comfy like an air plane seat or a couch can cause irritate a coccyx. U may go nuts trying 2 find a cause, but also in trying 2 relieve it. Lots of tricks 2 learn & cushions 2 try. Good luck.