Thanks for the post, I have also noticed this lately and thought it was just my phone. I recently installed the Thunder Live Wallpaper, thought that might be it so I changed back to a static wallpaper...now I know that's probably not it, but will leave it on static just in case.
The reboots are troubling, but I have noticed something that's even more of a pain: occasionally my touchscreen will lock up for no apparent reason. Phone and text still work for incoming, but I can't do anything else. The hard buttons work (volume and power), I can't turn the phone off as you have to select the Restart option from the dialog and it's frozen...is there a way to restart using some combination of hard buttons? Sometimes phone will "unlock" itself after a few minutes, but usually I have to do a battery pull...not recommended while you're driving! Anybody else notice this, and if so is there a possible fix? I'm running rooted stock 2.1, planning to go to rooted 2.2 once unrevoked 3 is back up. Thanks!