I neglected to mention the most basic issue with talking about Hashem’s middos, etc…is that they are all figurative. Hashem has no emotions or any other human characteristic; they are meant to be tools for us to understand on our level.
As for being selfish, we serve Hashem because that’s what He wants, but He wants it for our own good.
Wanting to be close to Hashem might technically, on some very obscure level, theoretically be selfish, but in practice, we have so much “yeshus” and desires for gashmius that if someone thinks that they’re serving Hashem for a reason above that, he’s delusional, and truly arrogant.