Tips for holding the guitar
 

I have a question for you guys.
I own a Schecter Damien 6 which I play mostly on my lap, and after a while, my picking arm bicep starts to get sore/tired. This will still happen even if I'm not playing anything and I just keep my arm rested in the picking position. (My arm also feels in an awkward position, feeling bunched up and my elbow behind me.)
When this happens, I move the guitar between my legs. Which I can play just fine, but I start to feel out of reach on the first 4 frets, leaving my wrist and hand in an almost awkward position to fret. So it's a bit of a stretch.

Does anyone have any tips for holding the guitar better?

We'd be able to help you more if you told us exactly how you are holding it.

Try to tighten the guitar belt. You could even try playing like Buckethead (hail him), I hold the guitar like him and it gives me much better finger agility.