Just an idea… but maybe nightmares? They start having them around this age. I’d try figure out what’s happening in her little world that could potentially be ‘scary’ and make a change. Could be as simple as a show she’s watching, I know someone who’s child was having nightmares from bear in the big blue house! My other guess would be a change in routine, I’ve noticed my boy thrives off of routine and consistency atm.
Go back to the ABCs and check; teething, sickness, sleep regression, separation anxiety, gas, constipation, too cold, too hot and if all that’s checked it may be unfortunately my least favourite doing it for absolutely no reason at all