I'm almost positive that it's lifter tick. It is really loud though, kinda like this: KNOCK, KNOCK, TICK, Tick, tick, tick, smooth. After sitting over night, I started it again this morning and it didn't happen again. Seems like sitting for long periods lets the oil drain to the pan completely. Then when started, it takes a second or two for the oil to make it back to the valve train. Never had that happen on any of my other cars before, and I've had some sit for 3 months at a time.