DD snores, squeaks, and makes all kinds of weird noises in her sleep. She's a quiet sleeper during the day, but at night because DH is such a light sleeper she's noisy, haha. I'm not worried, DD1 was the same way... She would create a new weird noise that would worry me on a weekly basis for the first 6 months of her life.
If you're worried about congestion... Sleep baby on his/her side vs back and elevate on end of the crib. I wouldn't use a nasal aspirator unless you can see lots of thick boogers clogging him/her up... Those things just irritate their noses and make things worse.