D.M.
Kari,
My son was in daycare for a bit and when the episodes like you described happened and after much investigation I took him out and found someone to watch him at home. Mine was a case of the teachers in the toddler "class" were never constant and this confused my kiddo.
But, now that he's 3 and started preschool his Dad and I came up with a routine at his new school of saying 'goodbye' before he's actually in the door. We do kisses and hugs outside and then when he walks into the classroom he's usually okay. But, there are some days when he does not want to go to school, and that's just a toddler thing.
Talk with your daycare provider and see if anything happened. Maybe a teacher left or a classmate moved onto a new room. It might be very simple, but see if they can offer some advice or tips on how they can help you both transition.
Good Luck.