Rattle on Startup

[Wrencher]

Greetings from a Porsche Noob.

I have aquired a '98 Boxster that belonged to an older gentleman that now has Alzheimers, and sat for about a year and a half. I replaced the tires, fueled it up, checked the fluids, replaced the battery and fired it up. At first, I thought I had the rare diesel model, but it did quiet down rather quickly and after bringing it up to temperature, and I drove it 20 miles with no further drama. It ran well for 180K, although the "check engine" light assured me there was "something wrong", and the "brake wear" light (red) pretty much gauranteed my certain demise!

Upon restarting it in the morning, I experienced the same "clatter" for 3-4 seconds, then it ran sweet. Same thing over the next 5-6 starts, after sitting for no more than ten minutes or so.

After searching this forum (I love these things!), I have found a bewildering array of potential problems and I'm wondering where to start. I have wrenched on everything from a Talon F-5000 to a Trans Am Tom Gloy chassis, So technical is no problem. Just want to find a starting point and decide the best direction to proceed. Any advice is well appreciated, thanks in advance!

Hans