[s-cars] Random metallic noise upon startup.

[Voits]

Listers:
Started my car after a week away and heard a distinct and rather loud noise,
so I shut down immediately.  After checking backside of tbelt with
flashlight/mirror (I'm due)for belt disintegration I decided to re-start and
guess what -- no noise.
Sounded like what you'd hear if you dropped 4 or 5  1/4" metal balls into a
blender at low speed: a random clacking, metal on hard plastic/metal to
metal sound, not at all rhythmic.  Have driven 200 miles since, many starts,
no symptoms.
Any guesses?
Steve V.
95.5 S6 54k miles