First Retic issue

[HP4]

I just purchased a male Purple Retic after I let go my Burmese. Although I love both, the Retic is totally different character. Anyway I have some questions regarding Retic care. First I bought him from a reptile store only 20 minutes away. I put him in a aquarium like tank like the one he was in at the store. Already have an Animal Plastics T5 but way too big for him now. The point is does he really need to be left alone for a few days? He seems very calm when I handled him once since purchase. He is in the first signs of shed but just cleared up. He does not act hungry at all, even though he's 4 ft he's pretty narrow. I've compared pics on the web and I'm sure he's too skinny ( 1 inch diameter). Second is he only stays on the heated side for very little time. When I handled him he was freaking ice cold! My Burm rarely did this. He's like always there and I'm worried this guy is suicidal. Any comments are welcomed. Just want to make sure I'm doing things right here.