Mine is like this at drop off and has always done it! Its such a fight to get him to go but he loves it there and chats happily about his day when he comes home. When i ask him why he just says its too loud but i do think its a separation thing as 5mins after i leave hes totally fine and playing happily.
When my boy started nursery he loved it, and took to it so well but they always said that wouldn’t necessarily last! Mine got a massive fear of the fire alarm which has impacted drop offs etc but we seemed to be getting through that after 6 weeks!
My nearly 4 year old is the same, just loves being at home/with us but then enjoys it when there! Must be separation.
I went through this phase a while ago, turns out there was a boy at nursery who had been bugging him and being really loud, once he told me I could speak to the staff and ask them to keep an eye out. Helped him learn to share a problem and then someone could help him Is he ok once he's there? Settled and involved?