happening to me, seemingly at random, htc one uk gsm. I havent modded or installed any roms or similar.
Clearing the data etc/force stopping or rebooting etc fixes it, but it appears again at some point.
I also have a strange extra entry in the call log, which is a newly created "unknown" outgoing call entry, timed at 5 mins exactly that gets updated whenever there is a call in/out to my phone. It's always there.
Anyhow, I will not reset my phone as i've only had it a couple of weeks. It's setup how i need it, and thus i will not go nuclear on it just yet. People have already said resetting hasnt fixed it for them etc.
I noticed also, that it's not connected to installing apps specifically, as it happens at times that new apps have not been installed. It also happens sometimes after app updates. I assume its an app that plugs into the contacts, syncing and whatnot so im hoping whichever app it is will eventually get updated?? Cheers.