Why does my lumia restart by itself after configuring vpn?

[Windows Central Question]

I use WP devel preview 8.1 for quite sometime and regularly update it, then last week I tried VPN (the one on setting -> VPN), added a profile, and used it. At first it was okay, but now my lumia seems to be getting random restart. Sometime it doesn't even boot up unless I plug in the charger cable (then after booted up I found out the battery is 50%+). Is there anything I can do other than resetting/using nokia recovery?

p.s: I've turned off VPN and deleted the profile.