I would swap the power supply with a known good one.
Let me tell you something....I've had that same exact behavior that you've described with your G23, but with the PS of a surveillance DVR computer!
I had to completely pull out the power plug from the back of the PS box...fiddle with the ON/OFF switch, plug everything back together then hit the power switch on the computer and only then I would see the PS fan come back on spinning again.....and yes....sometimes I would have to just leave it alone for a few minutes to get that fan to move.....at first I thought it was a bad, sticky fan but that wasn't it.
I ended up swapping out the PS with a new one and never had that problem again.
Your G23 basically, is just a computer....I'll betcha if you switch out the PS, the problem will go away.