If you wouldn't mind sharing your app list I would be grateful. I am storing apps on the microsd by default, and even went and purchased a new SD card to rule that out. Maybe the os/apps just don't like that functionality just yet. If I can't rule out an app I will try storing them all on phone.
I have a sneaking suspicion that there's an app that does not like being on the SD card. Most of them probably have no issue, but there could be one that may not like it. The first culprits I'd suspect are those that have not been updated in awhile. I don't know if there were any tweaks made when they supported SD card loading of apps in 8.1.
I've only had my phone for a day, but during that time it has not rebooted on it's own. I also have a Class 10 SD Card where my music and podcasts are stored. I'd guess that the rebooting problem presents itself early, so I'll wager that I'm not having it. So here's my full app list for comparison - but these are all in the phone's memory:
7 Minute Workout
7-Minute Workout
AFR
Alarms
Amazon App
Amazon Kindle
Analog Clock Tile
Audible Audiobooks
Backgammon Pro
Battery Saver
Bible
Bing Rewards
Bing Translator
Calculator
Calculator^2
Calendar
Camera
Coca-Cola Freestyle
Cortana
Data Sense
Despicable Me: Minion Mayhem
Disney Expedition
Facebook
Files
Finance
Financial Calculators
Flashlight-X Pro
Flixster
FM Radio
Food & Drink
Games
Health & Fitness
Help + Tips (beta)
HERE Drive+
HTC Blinkfeed
HTC Camera
HTC Photo Edit
HTC Sense TV
Hulu Plus
Internet Explorer
Jack of Tools Pro
Jetpack Joyride
Last Pass
Linked Inbox
Maps
Messaging
Messenger
Metrotube
Microsoft Solitaire Collection
Music
My Verizon Mobile
Netflix
News
NFL Mobile
Office
Office Lens
OneDrive
OneNote
PDF Reader
People
Periodic Table Pro
Phone
Photos
Podcasts
Preview for Developers
ProShot
Reading List
Settings
Shuffle Party
SkyMap
Skype
Snap Attack
Sports
Storage Sense
Store
Temple Run 2
Travel
Twitter
Verizon Messages Settings
Video
Video Highlights
Voicemail
Walgreens
Wallet
Weather
Weather Radar Live
Wikipedia
Wordament
WP UpTime
WPCentral
Yivosoft Recorder