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A few Things:
1. The couch may not be the best place for you, that depends on your couch and whatever is going on physically in your shoulders and spine area. You might want to invest in a proper chair for playing or try another place where you can sit with optimum posture for guitar playing. I bought a new office chair to play in. The arms can be raised so there is no obstruction. I do play on my couch also while I’m watching TV, but usually only for a few minutes at a time, then I’ll set it down. Also, my couch is firm and quite high off the ground, so it gives me plenty of support. You wouldn’t want to play in a couch that you sink into.
2. I would check out the warm up exercises (Daily Stretch for Guitar) here: https://tonypolecastro.com/skills/
3. Did you have pain in this area before playing guitar or is the playing that has triggered this issue? You may want to get yourself checked out.