My Roku turns on and off multiple times by itself with no warning. I will be watching netflix or playing my Xbox and it will just shut off, then on, then off, then on and will be fine for a little while then repeat the process.
Most of the remotes that come with a Roku TV are the simple (IR) remotes. If the batteries are a problem, it may send a stray signal to the TV.
Okay, things. Also try to ensure the power button is clean. It's really easy for dust and dirt to get into the area around the button (however small that is). Wipe with a clean cloth. Blow it out, breath or from a can of compressed air. If the power button is dirty, it can cause a keypress to be emulated.
DBDukes Roku Community Streaming Expert
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I have the same problem, it is not the TV because I have multiple Roku Ultra units and moved them around to see if it is the TV but it is not. It is the Roku itself. Will try the battery and don't think it is the on off button since it is new.