When you practice, do you do warm ups before you practice or just start right in? Also, what about the ergonomics of how you hold the guitar?

What I'm aiming is that, barring a medical condition that pertains to you that otherwise isn't common to most guitarists, is ther something that you're doing that might be creating the issue.

When practicing, I make sure that I feel like the guitar hangs itself from me with a strap and I'm just touching it to make notes. I don't want to be holding up the neck or pressing the body of the guitar against me too hard to hold it in place.