iPhone. 11 gets very hot and temp warning appears

Hi,

I have an iphone 11. From the time I bought it new it warm to the touch, when I checked online it said it was normal.

But the other day it has been hot to the touch and geting a temp warning. I also noticed the battery amount dropped 3 points from like 90 to 88 in a day. Also the battery dropped rapidly when this happended, like over a matter of about 30 minutes or so it went from 70% to 30% and continued dropping rapidly. This all happened over a two day period. I tried removing the otterbox to see if that was the issues, buying a new apple charger and cord to rule that out. But it didn't.

My questions is should I bother trying to a factory reset and losing a little bit of data (my last backup was 9/23) if this might fix it or not to bother and take it to repair because type of issue can't possibly be resolved with a reset.

Also could you tell me what can cause this issue? So I kind of know what I'm looking at finanacially. I know it might have a few things that can can cause it so you can't tell me specifically.

Is this fixable or worth fixing or should I get another? That's why I want an idea of the possible issue lol

Just a note, I keep my phone in a otterbox and take very good care of it. No water exposure, etc.

Edit: It seems like if I charge it a tiny bit and remove the plug it stops getting hot. Would it be worth trying a wireless charger? Could it be the charging port itself.

Thank Yoou