Pain in shoulder comes back on regular basis….?

Hi All wondering if you could help – I’ve got bad shoulder pain, gets worse at night but hurting more now during the day. It’s not necessarily when I move it, it can be while I’m sitting still – so no pattern in that. Doesn’t feel like muscle pain at all, doesn’t really feel like nerve pain. It hurts by the shoulder blade all of the sudden and then the throbbing starts and can last for hours…what does this sound like ? My hand can shake too but no pain in the hand…It may disappear in a few months, then come back every now and then which is why it doesn’t sound like an injury