What sort of hardware are you using? How much RAM, how fast & how many cores CPU? In particular, what type of drive is the game installed to (SSD vs mechanical hard drive)?
Small freezes like you describe (particularly when opening a map for the first time or accessing an NPC's store) sound like loading hiccups -- the game needs to pull additional information from disk and freezes while that's happening. Such load times should be nearly imperceptible on an SSD, but might indicate a problem with the drive if they're noticable. They'll be easier to notice on mechanical drives, but a hardware problem here can make them even worse.
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