Sometimes I Have Pain On My Right Arm About 5

Sometimes I have pain on my right arm about 5 inches above the elbow when I am reaching the back of my head when I am curling my hair..other times when I am reaching down and into a cupboard, other times when I am in bed and have put y head on my shoulder/arm I can have pain. Sometimes it is a very sharp pain and some a dull ache. Wonder whats up with that? I am 79 and I have almost perfect health. Jerene Jacobson