HTC Desire :: Re-starting In Night Since FroYo Update

Tried a search but couldn't find anything similar to what's been happening to my phone since I updated to FroYo on Sunday.Update went through fine on Sunday afternoon. On Monday morning at about 5am I heard my phone go off, picked it up in a sleepy haze and noticed the white "Quietly Brilliant" HTC screen, as if it has rebooted itself. Keyed in my security code and thought nothing of it, went back to sleep. Phone good as gold all day - no further issues on Monday.This morning, at around 4am, it did the same - re-started in the night, woke me up with a chime and the bright white screen. Keyed in the code, went back to sleep. Did the same at about 5am. The battery is currently about half full, so I don't think it's an issue there.I bought the phone about 2 weeks ago and didn't have any issues til I updated. The only setting I changed witin the phone was to have a security code set up for when it comes off standby. I've installed a couple of games since then too.Can anyone help? I'm going to turn my security code off and see what happens tonight, but has anyone else had this problem since the update?

I did notice a small icon in the top bar, sort of looked like an eye, but to be honest I was too sleepy to press it to find out what it was and it's now gone. No apps running on the phone, just WiFi, Bluetooth etc. Auto-update is set to on, which makes me think it's updating something? But why the re-boot?I don't mind it re-starting if it's meant to, it's just the fact it wakes me up at silly o'clock.