Faint rapping coming from the engine, kinda freaked out

[LoJac963]

I just hit 38k on my 06 and just heard this ticking the other day. My first thought was either idler or tensioner pully but it went away after a couple mins. I'm more familiar with the LS2 engine which is similiar and I know that engine never made sounds at startup. So as mentioned above it could just be our engines, exhaust mani, pully which I thought or something else.