He seems at little nervous

强烈怀疑是原句印刷错误,应是He seems a little nervous.而且如你所说,原句意思也是他有点紧张.
没有at little nervous或at little nerve的说法.即使有,little nerve也不会是如楼上说的“一点不紧张”的意思.
参照这个词组
have little nerve 没胆子,没胆量,胆小鬼
例句：
A:Hey,dare you jump from second floor?(Hey,敢从二楼跳下去?）
B:No...（不敢..)
A:Haha,you chicken!you barely have any nerve!(哈,你个胆小鬼!一点胆量都没!）
B:You chicken!You have little nerve!（你才胆小鬼!你才没胆量!）