"Random" computer booting problems

Hi there,
I recently installed 16 GB of additional RAM. Since then, sometimes my computer starts quite normally but sometimes it won't start anymore: When I push the power button, I hear the vans starting to work but after 1 sec or so it suddenly all stops. Then the computer will start countless attempts to restart but it will fail all the time. When I switch off the main power and try again after a short pause, I get to a screen where I have to reset or edit BIOS settings or load the "lask known good configuration" (press [F1], [F2] or [Alt] + [l]) anyways, I'll end up in the BIOS settings. Since there seems nothing to change, I press [Esc] and leave, wich will cause the computer to restart once again and either start to work normally or get into the endless reboot loop, again.
I've read about how the power adapter could cause such trouble or the additional RAM might be defect; but once the computer runs it will also run "under load". I can use the currently 32 GB of RAM and the computer will run just fine with high CPU usage and all. Hence, I wondered how the RAM or power adapter could be the issue when both seem to work at least some times.

What specific mobo, cpu, and RAM do you have?
Sometimes it could be a bad ram combination that causes booting issues like you describe

When you added the additional ram, did you buy the exact same set as the originals? If not, its most likely an incompatibility between the 2 sets. Different speeds or timings can cause instability.

My hardware: Intel i7-4790K CPU 4GHz, mainboard: MSI Z97-G43
Since the original RAM (2x Ballistix Sport 8GB 240-Pin DDR3 SDRAM) wasn't available anymore, I bought another set (2x Corsair CML16GX3M2A1600C9 Vengeance 2x8GB DDR3 1600 Mhz). The timings were the same, as far as I was able to find out...

All we can say is that mixing brands of ram is never a good idea but its possible the new ram has errors on it. Have you ran memtest? You may have to sell old ram and get another set of the new ram.

Try reseating all of the RAM modules and blowing out the slots. Pretty common that dust or debris gets lodged in the RAM slots.

I'm not saying that mixing RAM won't cause instability, but 9 times out of 10 mixing RAM works fine and it ends up just needing to be reseated.