Rackety noise from engine, my engine is rattling Options

[TRD_GT]

Hey guys,i'm sorta new on here,i havent really left any posts so this is my first one..

So..i've started to notice recently that when i'm driving and then come to a stop and the engine starts to idle,i start hearing like a sort of rackety sound,like a screw being bounced on a plastic table top or being vibrated on..its very minute and can only be heard from inside the cabin,the noise seems to be coming from the battery side of the engine..i cnt seem to figure it out..it only happens wen the car is idling..can someone please shed some light on my problem..

p.s. this site is awesome..i've learnt so many things about my car from website..best celica site so far..