I'm not quite sure what the case is, but after I fully turn off my N810 I have to do a hard reset (pulling the battery out for 10+ seconds) just to make it turn back on. Does anyone know what the cause of this might be?

Edit: Now it just seems random, after several attempts at holding on the power button it wasn't working so I typed up this post. Right after submitting it, I tried the power button again before doing the hard reset and it turned on...

Hunt around for the "power on problem", you're not the only one that has encountered that problem.