Last night my iMac i3 randomly shut down while I was watching a YouTube video. I tried rebooting and nothing. I left the iMac unplugged all night and this morning I was excited when I plugged it back in and heard the chime. It made it to the desktop, however, it wasn't long until it randomly shut down again. I tried resetting the SMC and get nothing. I tried another time and it booted up and stayed on a little while longer. I began browsing the web and it shut down. Whenever I press the power button, it sounds like the iMac is booting up, but it just doesn't. Is there anything else I can try doing? Or should I just take it in to the Genius Bar? Edit: I booted it up again, but this time the fans are blasting.