Hi everyone, asking for help again with my PC.
I am having issues with system booting up, I believe the issue is motherboard related...
If someone knows how I can fix the issue or has troubleshooting ideas please let me know.
Problem:
when pressing the power button I get no signal to monitor and system doesn't start.
It tries to restart multiple times, sometimes it success after 10~ minutes.
Started getting this issue after using Windows 10 for couple days, but I had jumped around Debian and Arch GNU/Linux and Windows 7 so that may have caused it... And its quite old pc...
Workaround:
Edit: no longer works 
I do get it to start when resetting with CMOS jumper. Then I am able to get to BIOS or continue to the OS just fine, but I have to do it every boot... Once system is running, it seems stable and temperatures are fine etc.
Troubleshooting:
I have tried booting without SSD, RAM and GPU, with different PSU, with new BIOS battery.
I already have the latest BIOS version.
None made difference, did not get beeps or anything.
Edit: Tried different RAM slots, setting BIOS time and flashing the BIOS, having no USB devices(only power and display connected), onboard video, dvi and hdmi. None made difference...
System specs:
CPU - i5 2500k
MOBO - MSI Z68A-G43
GPU - GTX 560ti
RAM - 8GB 1333MHz
PSU - 550W 80+ Bronze
SSD - 128GB
have you tried reflashing the bios?
Any overclocking involved, or just stock speeds?
I have not tried this yet. I try doing it with MSI M-FLASH in after a little. Thanks
Yes the CPU and GPU both are running with stock speeds, and temperatures seems fine.
Single 8GB memory dimm or dual 4GB modules?
Such kind of things sometimes happen wenn a memory module isnt seated properly.
I would suggest to re-seat the memory modules, or eventually put them in the other 2 slots.
Also double check if time and date are set correctlly.
These kind of things must be diagnosed step by step.
I have 2 sticks of 4GB, they are seated on the black memory slots. They both are detected when the system is on. BIOS time is incorrect rn. Didn't know it matters.
I try setting correct time and the other memory slots after the BIOS flash.
Thank you.
Yeah issues like this could be caused by manny things.
The best way to diagnose this, is to start with the standard things.
And yes bios date and time does matter.
Also on a side note, do you have manny usb peripherals connected to the system?
Okay I flashed the BIOS not sure if it completed because it tried to restart, also I set the BIOS time and tried different memory slots, I have tried without USB devices aswell... nothing seems to work. Thank you for your help, let me know if there is anything more to try.
Okay next thing on the list to try would be the graphics card.
You could try to reseat the card, and see if that helps some.
Another option could be to disconnect the monitor, take out the video card,
and connect the monitor to the onboard video port of the motherboard.
And check if that does change anything.
I have already tried with and without the video card, while connected to onboard. I also tried HDMI instead of DVI, no difference. 
Sorry i might have missed that.
Well then i have one other idea that you might want to try.
But its not the easiest thing to try.
Since you allready also tested with a different psu, i think that the psu could be excluded.
And double checked the power connections.
Try to reseat / reinstall the cpu.
hmm I did not try reseating the CPU, but I managed to get the CMOS reset jumper no longer working... Ill probably give up at this point and look into upgrading the system(CPU,MOBO,RAM) since there is no LGA1155 boards on sale at where I live. Thank you very much for helping with the troubleshooting @MisteryAngel
Well yeah of course your Sandybridge system can be concidered pretty dated for nowdays standards i agree.
It would be very difficult to find a decent replacement board for it nowdays.
If you have the money, then it might be a wise decission to upgrade.