This is about the desire to make love for the first time in a relationship. The line "This is not the Ritz whatever" is reference to the luxury hotel chain. "This isn't meant to be a backseat love affair" is implying that this is not about a one-night-stand, but rather the beginning of a meaningful relationship.
Will.I.am, literally dreamt up "I Gotta Feelin'." Said the Black Eyed Pea: "Have you ever had a dream where there's a melody in your dream? I'll wake up out of my sleep and record that! 'I Gotta Feelin' was one of those songs."