what do you think is wrong with it

[Brucelee]

When the Box sits for some time, the oil drains out of the lifters. When it is first restarted, they are quite noisy and don't quiet down until the car is quite warm.

Did you drive it and warm it up?

If you have no CEL on and no oil pressure light on, I would take it for a nice easy drive of about 30 minutes. After 10 or so, the engine will likely be back to where you want it.

If you see lights or oil etc. STOP.

Good luck.

[Jaxonalden]

I'm with Brucelee, if the sound is rythmatic it's probably a lifter that's bled down. If it is the lifter, it will "pump back up" after running a while.