Welcome!! Your baby is so cute, I saw the pics you posted in other thread
I just got my Strudel last Monday and he shivered a lot then too. He is perfectly fine now with me, but still shakes a little with my roommate and new people he meets. He also shakes when he's outside sometimes - its not that cold here (60's) it's from nervousness/unsureness.
Also the first day he was here he didn't want to eat much either. So I think a lot of what you are experiencing is normal and as he gets acclimated he will do these things less and less. I took Strudel to see his vet that first day. That is super important and helps you too because you can ask the vet any question you have