I heard an email drop on my EVO and about five minutes later I heard it restarting. What is that about!? Aside from hearing the email drop my EVO had been in standby for about 10 hours. Is my phone broken?
Unless it becomes a regular event... probably not. I have had this happen once (after having the phone for a month) while the phone was charging, the exact reason for the restart was not obvious but Android phones are computers. Remember when Windows computers used to crash all the time (Blue Screen) for no apparent reason?
If it becomes a regular occurrence you might want to try checking to see what applications you have installed and see what is running in the background.