"clung" sound when cold

[Solomon Ngan <"sngan@netaccess.on.ca"@netaccess.on.ca>]

Hi folks,
My '90 90q20v has a "clung" sound somewhere from the rear of the car
when it is cold.  The sound seems to occur right after up-shifting (but
not always).
It sounds "hollow".  After the car is running for a while (like 10
minutes), the sound seems to be gone.
As much as I think the sound is from the back, it may also be from the
front, at least, that's what my wife thinks.  Woman has sharper ears,
don't they ?
Any ideas ?  Does it sound like suspension system ? or muffler pipes ?

May I wish all of you a blessed Christmas and a safe holiday.

Solomon