Mine does 4-5 xs a day. I think all of them do to a degree. I've read hundreds of posts, tweets and comments about TB rebooting itself. Verizon and HTC are working together to fix it. But I have no idea when it will be fixed.
Well mines didn't start til this update came thru. Love my phone but i could have stuck with my Droid Incredible for this. Their basically the same phone just a few more extra feats on the Thunderbolt.