I concurr with the reset. I have been getting restarts frequently when I start navigator. In addition last night I noticed that my awake time on the phone was at 100%, though my battery still lasted throughout the day.
I did the reset this morning, reinstalled just a few apps and both the restart and awake time issues solved for now. Im of the opinion that too much crap residing in memory, as well as the possibility of bad app programming causes the restart issue. The restarts have become more and more frequent, though not to the point where it restarts by itself (at least not that im aware of).