Yes. It is completely normal. It is mostly separation anxiety. It may take time for him to settle. A lot of it depends on how he is at home. Is he an only child and has his parents full attention? Has he ever been left with another 'strange' adult? What type of parenting is he used to? Attachment parenting? There are many factors that will effect the amount of time needed to settle. I would just reassure him that you are still there and that not leaving. Try sitting on the floor with him and play and slowly make some distance once he is occupied.