I noticed a physical effect on me shortly after I got my 5g phone. I would keep the phone in my side pocket, and within about a month my leg right under the phone started to hurt - a combination of a burning feeling and a sort of a throbbing like when you can feel your pulse. Ultimately I bought a good leather belt pouch for the phone and made sure I always point the outer screen (I have a Samsung Z Fold 3) away from my body. The heat and pain went away.

I can't say whether my old LTE phone (Note 8) had the same effect because it came with a belt holster I used nearly all the time. When I wore shorts and put the phone in my pocket it never hurt but it was rare so I don't know if there would have been a cumulative effect.