My Nokia 6 randomly restart, it has happened twice since I bought it. Is this a self-protect mechanism or something? My battery is ok and it was properly charged when this happened.
I currently have Sec Patch from Sep 01 and Nougat 7.1.1
A mobile phone should not restart unprovoked.
(My Nokia 6 TA-1021 is solid since I bought it 6 months ago).
Nokia 6 should be on Android 7.1.2 and January 2018 security update by now.
Please connect to a reliable WiFi and manually check for OS updates, and manually check for app updates in the Play store.
Some other things to consider, in the order I would try if in your shoes:
1) An old or a cut SIM card? (Replace)
2) An old, or too slow, or possibly defective SD memory card? (Replace)
3) Apps and settings restored from a previous Android phone? (Hard reset and start fresh)
4) Third-party, possibly incompatible apps, installed from unofficial sources? (Uninstall such apps, or try run the phone in safe mode for a while)
A side note, just in case..:
Nokia 6 TA-1000 and TA-1003 are not 'Global variants' as falsely advertised in flea-markets online. They are Chinese variants, to be sold and used in mainland China and Taiwan only.
HMD Global should protect the Nokia brand better, but that's another story.
If the error persists, next step is a care point or the retailer.