I had the very same problem (on RC3). I later remembered that I just upgraded the radio to the latest version. Downgrading back to the radio in the 1.13 RUU (v0530) resolved the issue. My battery life dropped tremendously on the new radio as well.
On a side note, have you tried other ROMs since then? If it's happening in all ROMs it could be an issue there as well.
Nexus 5 (16GB; White)
Nexus 7 (16GB; 2nd Gen)