iPhone 4s getting hot I two days ago got a second hand iPhone 4s.
I notice that when I start using it, it becomes hot on top right side (if you look from front) and on left top side (if you look from back) near back camera and side steel too.

It becomes hot and battery also drops quickly like 9-10% in 12-14 mints.

I resetted the network settings too but it didn't solved the problem... :(

Please tell what should I do. I have no SIM card in it!! I'm using without SIM. I just turn on the Wi-Fi for some seconds then this happens.
Hot while using the phone is almost always a short. You might have it serviced if you think it's a fire risk.

Hot while charging can be a bad charger or a bad battery or a short, so you've got the easier problem to troubleshoot / repair.

Also - the age of these devices mean that the majority will be failing in one way or another whether the batteries need to be replaced or other issues like corrosion or just failure of another component has caused it to be out of design spec.