Shakespeare uses several different methods to create suspense. One is simple and nearly universal: being in the presence of death makes most people edgy. More dramatically, several plans or activities are still in suspension. We don't know if Laertes is going to move on Hamlet, if Claudius has another plan, and/or if something related to Polonius' body will happen. More directly, the diggers discuss if Ophelia will get a Christian burial or not (if she was a suicide, this was not likely), and Hamlet wonders about the identity of the body uncovered there. All these combine to leave us anxious and wondering.