Rebooted once when clicking on an address in a text message and it was opening the map accessing data via 4g. Just turned off bit strangley went straight to the thunder sound effect not the HTC green logo.
It would if somehow there were a short in the battery or of the batter door (extended life battery from HTC replaces the door) if one of the underside connections wasn't right.
That's where I was only it was more like 4-8x a day. I have today and tomorrow off so I switched back to the stock battery to see if it made any difference. It still reboots but not quite as often and I am going on almost 8 hrs of uptime the best I have had in a while and the sound of my boot animation is back after the phone shut itself off earlier today for no reason. *shrug*
EDIT: and it just rebooted after getting an email at about 7:53 uptime.