iPhone 6s saying support.apple.com/phone/restore

Follow the instructions here, If you see the Restore screen on your iPhone, iPad, or iPod touch - Apple Support

sillygirl ~ If "restore" messages continue to appear, it's worth checking the state of the battery...

Does your iPhone 6s Plus still have its original battery?

Also, what's the Maximum Capacity % here?...

Settings > Battery > Battery Health

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