iPhone 4S really hot

From the symptom, a failing battery, well within Applecare purview. Give them a call, they will tell you how to ship it. U will be wo phone for a few weeks.

 

Step 1 - eliminate software causes. Shut off ALL email/calendar/icloud accounts, shut down/restart phone and don't open any apps. Let it sit for 30 mins, see if it's getting hot again. If no, your problem is software. There are plenty of threads about fixing that.

Step 2 - replace phone. If you don't want the 2 hour drive, Apple can overnight you a replacement, but you'll have to give them a credit/debit card and they'll put a ~$600 hold on the card (To make sure you send back your old phone). I think they charge $25 or so for rush replacement, but it's nice because if you call today, you'll have your replacement tomorrow.

 

I've noticed my phone gets really got with just charging it should I be worried?

 

previously i used Otterbox case, and found my iphone very hot sometime, so i don't use it anymore.

 

first try to replace the battery