What are you doing with it? Where are you using it? It is impossible to even guess without information. Heck we don't even know whether it's a Exynos or Snapdragon model.
Things that generate heat:
* charging
* heavy CPU use
* large data transfers (mobile data more than WiFi, and I'm sure 5G more than other forms)
* the display, with higher brightness = more heat (using outdoors on a bright day with auto brightness will be the worst case).
If you are doing more than one of those things at the same time they add up.
If you are not doing those things, look in the settings to see what is using power - that should give some clue.
