I have noticed my Samsung Note 9 gets extremely hot (like you can't hold it while charging). There is really nothing that I have done differently. There is no pattern and it occurs with all chargers (wall, auto, charging block).
Any words of wisdom? It's worrisome!
Here are some tips that may help. https://www.samsung.com/us/support/answer/ANS00076952/ If the phone continues to overheat I recommend having it evaluated by a certified technician. https://www.ubreakifix.com/samsung