In reply to jasonpather:
Hi Jason, i suffer from a similar issue that short of flares up ever now and the . It is as you say, noticeable most when resting but loosens up when climbing. Unfortunately I cant afford a massage every time this happens but below tips help.
Get a stretchy band or light weight and do the exercises as indicated on UKC.
Google arm,shoulder, chest and lat streches and try these out when warmed up.
Buy a tennis ball and sandwich the ball between the sore spot on your shoulder and a wall (rough textured wall like brick works best) and lean against the ball. Go gently first so the muscle accepts the force rather than locking up. After a minute start rolling it around in circles or across the muscle. You may hit a trigger point (your eyes will pop out of your head if you do), hold the ball on this spot for 30 secs then work the ball around this area.
Buy a foam roller and regularly roll your back, arms, lats and chest. Lying on your back with the roller below your shoulder blades, cross your arms over your chest to hug yourself then rolling up and down brings alot of release.
And finally something new i have added to my training is scapula mobility exercises to improve my top line so when I grab a far off hold the load goes correctly through my arm and back and not uneccesarrily onto the shoulder joint. Google scapula press ups, scap, pull up and scap dips.
Good luck!