Good question! There are lots of songs that bring me memories, but Smooth Operator by Sade is the first that comes to mind.
This is one of the songs that my dad would always play on our CD player for me and my brother when we would fall asleep. It brings back memories when I would share a bed-bunk with my brother staring at the stars on my ceiling while slowly closing my eyes, filling my head with smooth music to dream with.