if your room is too hot it could be heatstroke. or if it's too cold your hamster could be going into hibernation. or if it's the day he could just be wanting to sleep. hamsters are creatures of evenings, night and early morning.
:{ i'm really sorry, but watch out sometimes, i don't think it applies to your case but if the room is too cold your hamster can appear dead but is actually in hibernation.
If your hamster throws himself on his back and screams like that, he still thinks of you as a predator and is simply terrified. You will have to start hand-taming gradually, moving slowly and offering titbits until he recognizes your hand as a friendly source of food. Please look after your hams...
if your room is too hot it could be heatstroke. or if it's too cold your hamster could be going into hibernation. or if it's the day he could just be wanting to sleep. hamsters are creatures of evenings, night and early morning.