I have exactly the same issue and was looking for answers with no luck.
My phone would hang/reboot randomly when running Waze (more often) as well as Google Navigation (less often).
I think this started shortly after the OTA update in January.
I tried removing apps, changing settings, etc, etc. - nothing helped.
This week I finally did a factory reset and... a clean phone with Waze and several other apps crashed when using Waze again
I've noticed, that right before the phone resets itself, Waze was saying "No GPS Signal..."
Since in my case the phone would crash with both Waze and Google Navigation, I would assume that the issue is with the phone OS/hardware... and since I did not have ANY issues in the first 1-2 month with navigation and crashes, the issue may be related to the January OTA.
All these are just thoughts. I'm still not able to reliably reproduce the problem. And when it comes, it comes when I need it the least - when I drive and need further navigation instructions...