iPhone 13 getting hot randomly

My Phone is 5 months old. currently on latest iOS version 15.4. Initially for 4 months I have used phone with case. Since last 1 month I am using it without case and what I am noticing that sometimes phone getting hot even though not preforming any extensive task. Sometimes while normal browsing on safari or sometimes even just clicking 10-15 indoor photos at normal room temperature it is getting hot(not warm) and uncomfortable to hold . Also each time when I felt this I have checked that there was no such app open/run in background that might be cause of such issue. One more app which is consistently causing this issue is - Instagram ! After watching reels on Instagram for just 10-12 minutes it starts feeling warm and if continue for more 10 minutes then again uncomfortable to hold.

I have uninstalled and installed Instagram 2-3 times at regular interval but no improvement. I am literally disappointed ! I know one more common suggestion will be phone reset but I don't think this will work as per my experience ! Is any one else facing such issue ? What should be done ?