Strange smell has followed me from my old apartment

Hello,
Hope someone can help with this. I noticed this odd smell in my old apartment in various areas, though the place was big enough I didn't pay much attention.
It has followed me to my new apartment.
The new place is about half the size. It was thoroughly cleaned and disinfected, and I even washed all the couch covers.

I noticed it in the new place on a few old boxes. Why boxes I have no idea. Now I have been gone for a month and it has taken over, or I notice it more when I go in.

It causes an instant stuffy nose.

It is somewhat relieved when I drench the air with vinegar.

It has a strange smell I haven't encountered- almost nutty, like nut butter that has been left out, or maybe an oily coffee. It doesn't really smell like mold exactly.

Is there a way to identify what it is specifically? I am concerned for when I go back. Not sure about throwing out everything I own.

Any help is appreciated
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