Okay, so recently I purchased a new motherboard (ROG Strix Z390-F) and CPU (i5-9600k) to upgrade my computer. I got round to building it the other weekend and since then have had some strange issues occurring. It started when my computer crashed to the blue screen twice in a day, firstly to MACHINE_CHECK_EXCEPTION and secondly to IRQL_NOT_LESS_OR_EQUAL. I had coincidentally that same day tried to boost my RAM Hz for the first time by enabling the inbuilt XMP ability in BIOS. Immediately after the two crashes I changed XMP back to disabled. The blue screen still continued to occur though, so I restored the BIOS to factory default (wondering if some settings XMP changed hadn't reverted) which seems to have cured the blue screen. But now, every time I boot my computer for the first time after getting home from work it says 'reboot and select proper boot device or insert boot media in selected boot device and press a key'. To get around this, I go into BIOS, then just save and exit without changing anything. From then it will boot to windows every time with no issue till the following day. I am absolutely baffled as to what the cause of all this might be, other than suspecting it may hardware related issue. I plan to do a Memtest86 scan tonight out of desperation, to see if this indicates anything? But otherwise I am hopeless. Any assistance this community can offer will be greatly appreciated! Thank you in advance for reading! My other hardware is: 16GB corsair vengeance (2400MHz), 650W EVGA power supply and a EVGA GTX1060 3GB incase that helps?