Mind of its own.

[Unclebobsuncle]

Ok. Hi, newbie here
99' F-350 drw with 7.3l I've been having an ongoing issue that appears to be escalating.
For a while, the radio would come on, on it's own, while sitting in drive. I messed around a bit checking wiring and put it down to bad radio.
Changing the battery terminls and batteries seemed to solve the problem and it been running fine for few months without issue.
Well the other night I was getting out of car and heard talking. Noticing the radio on in truck again. I got keys, got in truck and turned it off and left it. Until today. Batts were dead, I assumed from radio, so I put it on charge and let it go. After about hour of charging, suddenly the truck started cranking. Keys were in my pocket. I unhooked charger but it kept going until batt voltage dropped enough to not power starter. Puzzled I got in and started engine. Hadn't been used in couple weeks but started. Was a strang noise from engine, like a dry rubbing noise. Couldn't pin point it but sounded like from drivers side towards bottom. It eventually stopped but the. After a few mins, starter engaged again and started cranking, even tho engine was running. I turned off key and starter continued. I couldn't get the terminals off fast enough before it had again lowered voltage too low and quit.
Engine doesn't actually start, just cranks.
Any ideas? I was told may be the GEM which I assume is the ECM behind fuse Panel. Not sure how it unplugs but I havnt messed with it anymore. Hoping someone has an idea. Truck been running great up until now. It doesn't get used much but never heard that noise before. I'm thinking radio may be related.
Thanks . Hopefully can shed some light on this.

[NoRalPh]

The GEM has nothing to do with the starter though....

I'd be thinkin' about the Ignition Sw.