2000 379 starter (maybe?)

Here's what I got...Yesterday, pulled into a truck stop and shut the truck off while I ran in to pee. Came back out, key turned on, lights, gauges and warning lights all came on. Hit the start button, and notta. Checked the fuses in the kick panel, nothing blown. Looked at the relay, seems OK. Ohm meter across the normally open circuit as it shows on the relay diagram, so it's not stuck. Checked the wiring pigtail to the switch from the solenoid, nothing appears abnormal so far as post appearance or corrosion. Tried it again, and it fired up. Then on to today...
I stalled the truck at a light and immediately pushed the start button and got nothing. Now I'm sitting in the middle of the road and unable to start the truck. Pulled the same exact wire apart I checked yesterday and tried it again. Nothing. Pulled the relay back apart, nothing. Except this time, I noticed the wires in and out of the relay were hotter than I remember from yesterday and so was the relay. I also checked the pigtail going to the relay from the starter, those were stupid hot. Starter itself was not hot, so I tapped on it a few times to 1, make myself feel better by hitting something and 2. It's what Peterbilt told me to try. Still nothing. Pulled the dash out to see if maybe there was a loose wire in the dash, nothing I could see. All battery terminals are tight, all wires into the starter and solenoid are tight. And then the cop shows up and says he is going to have to get me a tow truck or I have to get it started. So, I get towed to the shop and I'm sitting here bored and decided to try the starter for fecal matter (it won't let me type the "S" word) and giggles...The #### thing started right up, no dragging or noises from the starter. And I have now started it 10 times with no hesitation in any attempt.
So, I'm leaning to the idea that the relay wiring is the culprit. Which explains why it's getting hot. Maybe a fusible link wire? Mind you, I am a licensed journeyman electrician, but not a mechanical 12v genius by any means. I get the common concept of a 12v system, but the starter relay wiring getting hot has me baffled. Anyone have any suggestion on what to look for and where to start (no pun intended)?

 

Well, it is most definitely the starter. Sometimes, the starter will only click, but if you keep tapping the start button, it will eventually turn. Other times it will turn, but only once like a low battery (batteries show 12.5vdc). Let off the button and try again and it turns like it should. Guess I'll be waiting to get the truck home and pull it myself to get it rebuilt... Anyone know a good place for starter rebuilds in Ft Worth?