I've just seen an instance where a Polycom Soundpoint 335 deskphone spontaeously re-booted. I have seen this a time or two previously, also. Checking the network logging on the switch, I can see that the port the phone is connected on changed its operational state from up to down, then returned to up in about five seconds - long enough to break PoE power to the phone and cause it to re-boot when power was restored.
Any idea what could cause the port's operational state to go from up to down for now discernible reason? Looks like there are other instances of the same thing in the network log, but I haven't checked to see if those have phones connected on them or not.