Question PC turns on for a brief time, then off, repeats

Jun 2, 2020
So, I've got a new problem that doesn't seem to be related to any hardware changes, since it cropped up in the last couple of months and I haven't changed anything about my system in awhile. I built this PC about six years ago, but a few parts are a little older and a few parts are a little younger. Recently I turned off the PC (which I don't do very often), and then when I tried to turn it back on, the fans would run and the lights inside would go for a moment, then stop, then retry. It's not always the same amount of time, but it's rarely long enough for any beeps or other indicator noises. Here's my build:
  • ASRock Fatal1ty Z87 Killer motherboard
  • Intel Core i5-4570 3.2G CPU
  • G.SKILL Ares Series 8GB (2 x 4GB) 240-Pin DDR3 SDRAM
  • MSI R7 260 1GD5 OC 1GB 128-Bit GDDR5 PCI Express 3.0 x16 HDCP Ready CrossFireX Support Video Card
  • LOGISYS Computer CS369BK ATX Mid Tower Computer Case with 480W Power Pupply
  • SanDisk SDSSDA120G SSD Drive (my C: boot drive, ideally has just my Windows 10 OS on it, but it's been filling up lately and I'm not sure why)
  • Three Western Digital internal Hard Drives
    • F: (1TB) is where I install all my programs
    • G: (2TB) is storage
    • Z: (2TB) is also storage
I've followed various threads and fixes I've found here and elsewhere online, and here's an incomplete list of what has worked but not reliably:
  • Disconnecting all drives except C: and restarting - works pretty reliably, but not very practical
  • Disconnecting all drives except C:, then reconnecting one drive at a time - This worked with G: and Z: but ran into problems with F:, which led to...
  • Connecting F: to the motherboard with a different SATA cable - This seemed to fix the problem (though I went back to not restarting my computer regularly too), but today when I shut it down to replace my temporary SATA cable with a new permanent one, the problem came back before I made any changes
  • Removing the motherboard battery for awhile, replacing it, and restarting - This I've mostly tried in combination with one of the tactics above, since it's been unreliable on its own.
When the system actually boots up, it's running perfectly. It's just getting booted that's the problem. Any ideas?

Thanks in advance!
Jun 2, 2020
check cpu temp? fan spinning?
how old is that 480w? it that come with the case?
All the fans work fine when the computer is running, and at the very least the two case fans and the fan in the power supply turn on for that brief moment when it's trying to start (I can't remember if the CPU fan turns on then too, but it runs when the computer is running).

Right now the CPU temperature is fluctuating between 48C & 53C, Motherboard temp is 35C, CPU fan and the two chassis fans are running, but the power fan is reading 0 RPM. I'm pretty sure I've felt it run in the recent past when I've checked it, but it doesn't seem to be running now. The power supply is original to the case, so it's about 6 years old now.