How do I get my 1996 jaguar Xj6 back running

What is your question?

Ok I have a 1996 jaguar Xj6 my car first gave me signs when it struggled to crank when it cranked at that particular time so when the temperature was on cool it drove like a champ when it was in between both temperature hand like a normal car would drive it would get hot after a while what I mean is that the temperature hand was in between both temperature hands and still ran hot it would literally stop itself when that happens my steering wheel get very hard like I have no power steering sometimes a transmission light comes on at the top left corner i used to check my tailpipe and it was redhot when my car suppose to ran hot i dropped STP gas treatment in it and it rode 100 percent great again I thought I'd fix the problem with only 4 dollars i was so mad at myself but anyways after that my car wouldn't crank again come to find out i had a dead battery so got a new battery car won't say anything when I turn the ignition over another thing my radio be hot too it would get hot befor car

What makes this problem better or worse?

Spt gas treatment made it ride better

How long has your 1996 Jaguar XJ6 had this problem?

Every since I had it like 8 months on and off