For Some Time I've Had Sensations In My Right Arm

For some time I've had sensations in my right arm - not pain but kind of like it tingling and the kind of sensation of having a limb "fall asleep". Not to often at first, but pretty constant over the last couple of weeks. Very itchy skin in same areas - from wrists to shoulder. Now starting to get pains akin to having a sore muscle from use, but it is not from use. Happens often when I sit down and then will go away if I shift my position - sometimes. Comes and goes......not constant. Never experienced this before.