Disk playback works just fine without an Internet connection. I use mine that way most of the time, but the streaming video features that this player also offers, such as Netflix, will require an Internet connection. The disk player detects, through its HDMI connection, if the TV set has been turned off and it will turn itself off. It will also eventually turn itself off if it is not being used, but mine has never turned itself off while I was watching a DVD movie.
My BDP-S185 is only sporadically connected to the internet (if that's what you mean by "a computer connection"); it's great for disc playback and for playing files off an external HD; and no, it does *NOT* turn off every 30 minutes under normal circumstances--if you have a video *paused* (or if it's playing nothing and just sitting idle) for a few minutes, it goes into a screensaver mode; and then AND ONLY THEN (with a video paused or sitting idle), after 30 minutes of no button presses, it will turn itself off; it never turns itself off if it's playing a video. Hope that clears things up.
We use our BDP-S185 only to watch movies. The unit is not connected in any way to our computer or to the internet and it works just fine. I haven't experienced the 30 minute shut off issue. I guess that is only if the unit is inactive, that is, not playing a movie. Hope this helps.
Playback-only is probably the most common use. Some discs now have other features that would require internet connection, but that's probably not why you bought/rented the disc to begin with. As far as the auto-off, I have never heard of it. It's not clear from your question: are you referring to some kind of timer that works if you leave a disc on pause for too long? Because a 30-minute auto-off feature would not make sense if you're watching a 90-minute movie.
This is intended to hook up to a tv or a/v receiver, which is where you will see the functional menus. If by computer connection you mean "internet", yes, internet is not needed for this to work just fine. No, it doesn't turn off after 30 minutes while playing; not sure if it goes into a "hibernation" state if its on but not being used.