What Causes Stiffness In Neck While Sleeping?

For aprox 3-4 months I ve been having stiffness in my neck while sleeping. It has woke me and the pain is sharp. I wake with the pain at all hours of the night and I will have trouble getting up from the bed.ive tried different pillows and sleeping on my side or back. Regardless I still have the neck pain. Is there anything else I can do?