Just started yesterday-All in One flickers then turns off, like asleep  

Hi. I hope this is right sub-forum and that it is okay to ask here though I dont know if the issue is specifically related to Windows (though Yes, it is Windows 10 on it) or not...

I have a Vaio all in one desktop VGC-JS210J. It's used daily for simple things such as browsing. The only display problem it's had is sometimes it would suddenly go black then immediately come back on. It usually only happened after browsing for a long time or if Edge got opened, so I chalked it off to needing more memory probably.

It was working fine yesterday, then when sat at it about 30min later the screen wouldn't come on. I've found out that I can hit the sleep button on keyboard and after it goes into sleep (hd light goes off & mouse sleeps), I can wake it then by hitting any button. I get my screen back for anywhere between 10sec - 5 min (usually about 20-30 seconds), then it suddenly goes black like it's been turned off again. That is the ONLY way I can get it back on at all though. When restart it, it often stays on for about 45 sec - 2 minutes. I've noticed today that it often flickers before it turns off.
Any clue?

Also, since it's an all-in-one, can I hook a separate monitor to it and use it?


P.S. Yes, I've tried it in Safe Mode too, but it still does it. I've also checked device manager but show no issues. (To get to those settings it takes billions of times of hitting the sleep button, waiting for it to go into sleep, then waking it)