My iPhone 5c sometimes won't wake up, or the slide to unlock is unresponsive, forcing a reboot. I have had each problem twice. It isn't a little freeze-up where it will work later; it's just dead or won't unlock. Forces me to reboot.
That's the same things that's happening to me because I also have a 5c. I don't know if I should do a fresh clean install of iOS 8 again and set it as new or something. I talked to a friend's who also had iOS 8 beta on iPhone 5s and he has hardly any problems. Hmm