Is she teething? I know some kids have it really, really tough when this is going on, and molars are the worst of it. Is there anything new in the environment? Have you been away from LO more lately? Anyone been sick lately? I'd just look at things like that.
My 28-mo. dd is sleeping okay, but is needing to play "little baby" where I treat her like an infant for a little while almost every day. She wants me to wrap her in a blanket while we nurse, for example. Or she climbs in a laundry basket with a blanket and calls herself "little baby," wants me to rub her tummy and sing to her. Then she's done w/it for the day, usually. I just think she's developing cognitively and there is some fear that comes w/growing up. Maybe your LO is just having this extra needy time at night?
HTH