Is it time to replace the motherboard?

My PC keeps losing power randomly as if I had hit the main power switch. It stays off for just a second and then turns back on again. It happened today and then once it turned back on the lights and the fans came back but it struggled to actually boot, never connected to keyboard or monitor. I opened it up and reseated the ram sticks and turns out one of them in a2 will let the computer successfully boot as normal but the other one in a1 as well or in a2 by itself will not. It just sits there with the lights and fans and the dram light on. Right now the working stick is in a2 and the VGA light is white and everything seems to be fine. Is it time to replace the ram stick or motherboard or is there something else I'm overlooking? The PC is like 5 years old at this point.