Hello, just got myself a Note 3 a week back and a bit frustrated as my unit will go to 'silent vibrate' mode by itself and will go to normal mode by itself after some time.

I have had exactly the same situation with Galaxy S2 but was resolved after performing factory reset (after flashing Jelly Beans).

Applied the same workaround on 2nd day of using Note 3 but it is still behaving the same way ... damn !!!

After looking the defects section, looks like am the only one facing this problem and is anyone facing the same fate ?

... going to email to Samsung shortly.

s2 resolved after factory reset and just using standard apps from PlayStore.