There can be a lot of reasons for shoulder cramps and shoulder pain when you are running, some which aren't very serious and some that are very serious.
If your shoulders hurt, then it is probably worth seeing your doctor or physical therapist to make sure it isn't one of the more serious problems such as a problem with your heart (cardiac angina) or spleen, or some sort of bursitis or spinal problem.
More than likely, it's just a minor muscular imbalance or weakness or a minor issue with your running form that a coach could help you correct.
Here are a few things that you can try to see if they provide relief:

1. How old are your shoes, and are they the right shoes for you? Have you ever been fitted? If you are wearing the wrong kind of shoes for your running style, it can throw your body out of whack and cause seemingly random problems throughout your body including in your knees, hips, back, neck or shoulders.
   
2. Do you clench your fists when you run? Try loosening up your grip if so and see if that helps.
   Pretend you are carrying an egg that you don't want to crush if you have trouble keeping your hands loose.
   
3. Stretch out your back and shoulders before and after every run.
   You can rotate your shoulders forward and back by swinging your arms in circles, roll your head clockwise and semi-clockwise, invert your arms and lock your fingers both in front of and behind you and reach as far forward or back as you can, and roll out on a foam foller.
   (I would recommend the foam roller even if you weren't having any sort of cramping or pain.
   )
4. Start building more strength.
   Running requires more upper body strength than you would think, especially on longer runs, so some simple weight lifting for your cross training days can lead to some rapid improvements.
   If your shoulders are hurting now you may need some time off to let the pain go away depending upon when and how much they ache.
   Pushups are a simple exercise that you can do anywhere that don't require additional equipment; pullups are also a good exercise if you can find a bar or branch somewhere that can support your weight.
   If you do have access to gym equipment, then I recommend dumbbell bench presses and dumbbell rows.
   You want to stick to body weight or light weights, with dumbbells and free weights being preferred so that you have to use more than 1 isolated muscle group to help your muscles get used to working together.
   
5. If you experience any sharp pains or the problem doesn't go away, visit your doctor or physical therapist who can accurately diagnose what is going on.