I've been having these on my iPhone 6, iOS 8.3, just the last two or three days. I've had at least a dozen. I only see one diagnostic log though, a JetsamEvent about ten minutes ago.
Don't recall having issues with reboots yet on my iPhone 6.
Lately issues with iPad Air 2.
Doesn't load Internet. Seems like an issue when updating apps.
Today I Was listening to music and it just rebooted.
8.2 and before didn't have these issues. New since updating to 8.3. Probably 5-8 reboots so far. Ugh.
Been happening since day 1 of release.
https://discussions.apple.com/thread/6550902?start=0
It mostly happens with 128gb models and the number of apps.
A few sites say it's because of the the triple level nand flash.
Seems to be more stable on zoomed view if that helps.
I've started having springboard crashes on both my iPhone 5s (32 GB) and iPad Air 2 (128 GB) recently (both on iOS 8.3).