Why is Gatsby nervous when Nick sees him at home at 2 am?
The scene to which you are referring takes place at the beginning of chapter 5. Nick returns home at 2 a.m. from an evening out to see Gatsby's house ablaze with light. Gatsby seems to have the lights on in every room of his spacious mansion. Gatsby, seeing Nick pull in his drive, comes over to speak to Nick and his mannerisms show his nervousness. Nick tells him that he has spoken with Jordan and Jordan has asked him the favor that Gatsby asked her to ask of Nick, namely, to invite Daisy over for tea. Gatsby is nervous because as his plans and hopes of reuniting with Daisy get closer to actuality, the reality and excitement are getting to him. It's been five years since Jay and Daisy have seen one another and Jay loves her every bit as much as he did when they parted five years ago. Everything he's done in the last five years has been with one goal in mind: to get Daisy back, and now, his goal is in sight. He has the lights on in his house because he's trying to see if it will pass muster with Daisy. Gatsby desperately wants her to see him as worthy of her and her social and economic class. He believes that as long as he has the trappings of wealth, he will get Daisy. He wants to be sure that everything in his home is perfect and displays his wealth.