Phone cycles to home screen, then powers off. Ideas?

[SimonSays]

So I just got this phone a couple of weeks ago, which I had no issues with for a week or so. Now, the phone, at various times, cycles to the home screen, then powers itself off. It continues to do this until it just magically seems to fix itself and run fine again. I updated to 2.1(official from google), thinking it might fix this issue. But, as soon as the phone powered on from the update, it went through this cycle and has been now for about 30 minutes. I've tried simply pulling the battery and letting it sit for a minute, but to no avail, it continues to do it.

Has anyone else had this issue and if so, what is the resolution?

By the way, I work for a Verizon retailer and have had quite a bit of experience with these phones. I don't think this is a noob error.

Thanks in advance!