Motorola Moto X — Marshmallow updgrade Problems....and others.

I've a new Moto X Play which in the week I've had it initially impressed. There are numerous problems though. the first headache is that when I tried to update the OS to Android 6, I get a message saying, " Authentication problem....try again'

and now when I try the download the phone switches itself off and then tells me Android is starting...along with the black screens and various logo's with the final 'Gmail has Stopped' window as an added insult.

The phone has also taken to turning itself off and then on again...the last time it did this it altered the screen wallpaper and I'm now back to default.

Add to this that it tells me that Gmail has stopped and do I want to report this and I'm wondering if I've got a duff phone.

My old Moto G had non of this nonsense and my move to a better phone is not proving that....Anyone with any ideas?