4 Month Old and Separation Anxiety?

My son has always been a little uncomfortable in new places, and will become fussy after a few hours until we're home. Lately though, I can't leave him alone with someone else for more than 20 minutes without him crying constantly. His father and I are the only ones who can calm him, or when we're at home. This sucks because we're in the middle of moving, and he isn't used to the new home yet so it's difficult to calm him. Not to mention, I go back to college soon, and he's not used to the new nanny we hired 🙄 He is definitely developing separation anxiety already, which seems to be early, but how can we help this? I know how to handle it with toddlers - I'm a Social Worker with a Psych background - but these don't exactly work with an infant. Anyone have any tips?