Gluten makes the dough stretchy and elastic and needs time to develop. If your pizza dough is shrinking back when you try to stretch it, this may mean that the gluten hasn’t had time to develop. Proof the dough for longer to relax the gluten strands. Alternatively, the dough could be too cold. Bring it back to room temperature (gluten is tighter when cold and this will cause the dough to spring back).