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Your Sammy sounds like a normal puppy to me.
The only thing I feel is different is the banging of his head on the floor.
I would have him checked out by a vet.
As far as hiding in a dark corner, they like to do this. Buddy goes under
the chair at night, always did. It's his sactuary. Your pup is only 5mo.
old. He will be hyper, he's a puppy. Don't take away his toys, he needs
them to relieve his energy. Do you walk him at night? Do you play with him
during the evening to help him burn up some of that energy?
He's sounds much like Buddy as a pup. Bud use to jump on my head
during the night and wake me up. I kept a magazine under the cover's and
swated him with it from time to time. He learned after a while that you don't
wake me up to play during the night. They don't want to sit still, be patient
this comes with getting older, maybe around 1yr old. Don't expect too much
from him now. You should be working on sit, stay and come along with other
tricks. They love to work and learn. I think your expecting way too much
from him at this time. You have to exercise him and make him tired for the night. Some pups a laid back and don't like to play others can't get enough.
If he checks out ok from the vet, enjoy him and teach him tricks, long walks
and he will settle down in time.
Enjoy and good luck.