My Roku keep turning off and going back to main screen in middle of a movie

Hi, LindaBW 

Greetings, and welcome to the Roku Community.

We understand the issue you have experienced with your Roku device that keeps turning off and going back to the Home Screen while watching content, and we're here to provide instructions to troubleshoot the issue as well as update your Roku device. Please refer to the information below:

Use the Settings menu to perform System Restart.

On the Roku remote, navigate to Settings > System > Power (skip if you do not see this part) > System restart > Restart.

System Update

Follow the instructions below to manually check for software and channel updates.

1. Press the Home button on your Roku remote 
    
2. Scroll up or down and select Settings.
3. Select System.
4. Select System update.
   
   
   • Note: The System update screen displays the current software and build version, along with the date and time of the latest update.
     
     
5. Select Check Now to manually check for updates.

If there is new software available or there are updates for your channels, then your Roku device will download and install them automatically and once completed, your Roku device will reboot.

We hope you find this information useful, and feel free to reach out to us if you have further concerns or inquiries.

Best wishes,
Kash

LindaBW 

With newer Roku devices and newer OS, the settings may have moved around a little bit from those mentioned by RokuTakashi .

The System Update is the same as a Software Update.

Settings/System/Software Update

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The System Restart has also been relocated on newer devices.

Settings/System/Power/System Restart

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In addition to the suggestions mentioned above, try disabling your Auto Power Savings (Settings/System/Power/Auto-Savings/20-min inactivity) and see if that helps your issue.