I'm from America, therefore I speak American English, I suppose. But I'll put in my personal experience as a basis of opinion: I've never heard any naturally English speaking person use the verb "to be nerved", or anything of that nature. It's a mistake I came across a lot with Germans learning English, they always mix it up when saying "He's really nerving", or "I'm so nerved". I would say, to be best understood by every naturally English speaking person, it would be best to just say "I am annoyed", (as a sidenote, that I just thought about, "I'm bothered" could be a good synonym for "I'm unnerved". I think Susanna had said it correctly, when she said it was something that bothers you, or that is eerie, so much that it makes a person wary, or uncomfortable in the current situation....although "bothered" could also mean "annoyed" if the correct emotion is connected to it, if you feel angry to some extent, or in the least displeased, then you could be bothered (meaning annoyed)).
I've just begun learning German only a year ago, but I'm quite good with English definitions and other aspects of it. Therefore I won't try to give a translation to all the English I've just written, if someone feels up to it, I'd appreciate it.
And one last thing, "to nerve" someone, being that I've never heard it, is not at all a saying that native speakers use; only "to have nerve", meaning that someone is brazen, or not take others' feelings into account when doing something.
Wow, this is long, anyway, in closing....Don't use "to nerve" as a verb in English, only unnerve, as I've explained in the former paragraphs. Hope this helps to clear up (at least the English side of this string) everything.