[Feufeu47]

I've also a Galaxy J6, and after an update of Android, i restart the phone but i've a black screen with the unusual request of "password to start android".
I've never had a password to block my device and there was no sequence also;
what can i do (other than a hard reset)?

[methodman89]

Do you not know your lock screen access?

[mustang7757]

Hi, welcome to AC!

Can try go to here and remotely unlock your phone if your sign into your samsung account on the phone . Otherwise factory reset in recovery.

https://findmymobile.samsung.com/

[B. Diddy]

Welcome to Android Central! Has this always been your phone, or did you get it from someone else?

[Feufeu47]

Nobody use this phone before me.

[mustang7757]

Your only option is factory reset

[B. Diddy]

The need for a password wouldn't suddenly appear for no reason. If you never created one, and you bought the phone brand new from a legitimate retailer, then the only other explanation would be a major system glitch.

Where did you buy the phone? Was it directly from the carrier, or from a major retailer? Or was it through eBay, or perhaps a 3rd party seller on Amazon?

[Feufeu47]

I bought this phone in a large retailer. The box was closed and everything new.

[B. Diddy]

You already tried the Find My Mobile technique that mustang7757 suggested?

Every so often there can be a glitch with an update, so it could be that. Another possibility is that the retailer actually sold you a phone that somebody used and returned, and they didn't bother to properly remove the previous account and reset it (it's easy for a store to reseal a box and make it look like new) -- so you could also bring the phone to the store and ask them about it.