Your screws are loose! No silly…..your screws are actually loose. How do you fix that? You could use bigger screws so that when tightened the threads are bigger and are able to grab the wood or you could use the same screw. Old timers would use hardwood toothpicks. You can cut them down in size and stick a couple of pieces in the hole. When you tighten the screw the wood jammed in the hole will be pushed against the old threads and the screw will tighten. No toothpicks? Find whatever you think will work and stick it in the hole. Here we used a pink zip tie. Seemed to work just fine!