Why does the radio on my 2008 Kia Sorento turn itself off when I turn the ignition off, but doesn't turn back on when I restart the car?

Recheck wiring

Sounds like you need a new ignition switch if key won't release

its in in the FSM.
and at alldata,com
if stock.

you should take it to be checked by an electrician it might have some wires touching each other

First off have the battery tested, just because it has enough juice to light the dash and the radio doesn't mean it has the 100 amps needed to run the engine starter motor. Autozone and others do battery testing for free.

We experienced an intermittent problem where the entire audio system on our new 2013 Kia Sorento would fail to turn on at all after a brief stop (at a thruway rest area) on a long trip. When it happened twice the dealer replaced the entire unit and we had been trouble free for almost a year when my daughter reported something flaky happening to the radio recently again. I am keeping me eyes on this problem once again.

Try giving the stering wheel a pull or push whilst turning the key ,the lock is into the wheel and its needs releasing thats all ,ask a man to do it for you

correct check the relay ck them some of them are inter changeable with in the fuse box under the hood just verifiy the imprinter number are same and circut direction is the same

Sounds as if Somthing is IN the KEY LOCK CYLINDER, I have had Customers that have Children that Stuck things into the Ignition Lock.
This Usualy Requires Replacing the Ignition Lock Cylinder itself.

http://www.kia-forums.com/kia-sorent...removal-2.html