That's quite normal. It takes awhile for any type of animal to settle into their new home, to get used to things. This usually takes about 2 weeks with reptiles, so you're right on schedule.
Just continue handling it, at least once a week. Your snake may even strike at you, bite you before its over with. Some do, some don't.
The tail rattling is what a lot of colubrids do to mimic a rattlesnake. A lot of times they're bluffing, trying to intimidate you to leave them alone. You'll find that if you'll just go ahead and get them out they'll most always calm right down.
I recommend continuing to hold them when they get restless, starting to move about more. Before long you'll learn how to let them crawl thru your fingers/hands without letting them actually go anywhere. Most corn snakes are somewhat hyper, constantly on the move. They won't just lay around or move slow. However, they make great pets, for beginners & experienced keepers, alike.
I've got a 4ft wild-caught corn that I've had for almost 3yrs now. I handle it about once a week and it hasn't bitten me since the first day I got it. But it still loves pretending to be "Billy Bad" by rattling its tail when I walk by sometimes or even occasionally striking at me as I walk by. It will look pretty mean rattling its tail even when I reach in to get it but the moment I pick it up it practically melts in my hand, becoming sweet as chocolate.
Don't be afraid of your snake. Put on gloves & long sleeve shirt if you'll feel better, but don't let it have its way. Show it who's the boss. You're in a defining moment. They rarely bite, but sometimes they do. If they do it doens't hurt and they usually don't bite more than a time or two if they see it doesn't work.
Hang in there!
HH
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Due to political correctness run amuck,
this ol' hillbilly is now referred to as an:
Appalachian American