buzzing sound at initial drive? Help..

ok, so i've been noticing this funny sound..like a short buzzing sound (1-2 seconds) everytime after i start the car and drive..like for example i start it, hit reverse, then drive..after a few feet i'll hear this buzzing sound...at first i thought there might be something underneath that's caught up like a plastic that's rubbing off...but there aren't. this only happens at start-up...like every morning or after gas fill-up...so i'm pretty much clueless where it's coming from and not pretty sure if this is a big concern...i was kind of suspecting it might be coming from the transmission but mine shifts pretty well and runs smoothly...anybody had this problem/ issue before or something i should look into...thanks in advance...

my car is a 99 civic EX AT

do u have a amp in ur car ?? mine did the same thing but it was because i had the amp switch to high's... i would step on gas and it would just buzzzz untill i switched it back to low's...

amp? as in for stereo amplifier? well no..i don't..unless you mean some other thing...please inform me..

thanks for your reply. i hope it's not serious..

yea that is what i meant... if not then i don't know...