As noted above, I've been looking into this issue for quite a while. If you Google the issue, you'll see that it is pretty widespread (though I know most of you probably only experience it here):
https://www.google.com/search?client=safari&rls=en&q=safari+crash+and+reload&ie=UTF-8&oe=UTF-8
The issue only occurs with Safari, or at least I've never had a report of it happening with any other browser. It may be related to memory usage on your device which would explain why it seems to happen more on iPhones.
If you have a rash of these crash and reload incidents, you might try force quitting Safari (if using iOS) to clear the memory.
I have learned a couple of new troubleshooting techniques that I plan to test today.