Trigger points are common in all the main shoulder muscles. In fact just about all of us have latent trigger points, usually as a result of poor posture .... one of those simple things that they used to teach in schools but has long ago vanished.
Failure to work on our posture and to take simple steps to promote shoulder health will often (increasingly often) lead to active trigger points, and a whole host of potential musculoskeletal injuries as you get older.
So if you spend anything like the time that you probably do leaning over a laptop, tablet, or adapting your body to talk on a mobile, take note of these simple stretches. 10 minutes a day could save you a whole lot of trigger point bother further down the road ...
Stand with your arm out and your forearm pointing upwards at 90 degrees. Place a broomstick in your hand and behind your elbow. With your other hand pull the bottom of the broomstick forward.