Exchange it since you are within the 30 day period. Mine restarted a few times during the first couple weeks. I tried a few things and then it was fine. Then about a week after the 30 day trial period was over it lost its mind and restarted three times in one day while I was on a call. Because I thought it was temporary and waited too long, I ended up doing the warranty exchange. My replacement Curve (which is surely a refurb) actually works much better but I would imagine that you would rather replace your new phone with another brand new one while you still can.
Mine restarted primarily smack in the middle of calls, though it restarted once while surfing the web. I've had my replacement three or four weeks now and I've not had a single problem. The warranty exchange was painless actually but I wish I had jumped on it sooner and just exchanged in store.
I love my Curve, especially now that I have a correctly functioning one.