Transporters work by de-assembling something (e.g. you) and re-assembling it somewhere else. What if, when you're dis-assembled, you die, and the re-assembled version of you is essentially a copy? Then every time someone steps onto a transporter, their final thought before death is that they'll end up beamed somewhere else. And the re-assembled version (copy) just thinks that everything went fine and continues on like nothing bad happened.
“No one ever steps in the same river twice, for it is not the same river and they’re not the same person.” - Heraclitus
What if the feeling that you are the same “person” as you were yesterday, or even as you were 5 seconds ago was illusory all along? What if you “die” and a new you is born many times a second all the time?
There’s also a Ship of Theseus thing going on here since your cells are constantly being replaced by new cells. At what point do you stop being you and are simply the train of thought that carried over from your old cells?