C.H.
My middle daughter went through the same thing, from about 18months through 3. My stratigy was to just speak softly to her and try calming her the best I could, by rubbing her back or stroking her head ( if she would allow me to). I would also repeat her name in a soft voice to try to wake her. She sometimes responded to her dad better so we would switch off if one of us got frustrated and sometimes this would work, just the sound of a different voice snapped her out of the terror. They seemed to ease up as she got older but when she was very young they happened quiet frequently. I know what you are going through and I wish you good luck