Automatically shutting down

From day to another I heard at night my pc starting itself, i turned it off, then after 30 minutes it started itself again, so I turned off the extension cord. I used to put it in sleep mode a lot. In June sometimes it woke up from sleep mode, after I shut it down every time and unchecked all...

Hi, I'm a first time pc builder and just finished putting it together. When I turn it on, all the LEDs/fans start working, but no image displays on the monitor. I've tried unplugging the gpu, plugging the hdmi into both the motherboard and gpu port, and have already read the guide to issues like...