Have you tried a bios reset?
Yes, it boots with 2400Mhz, 1.224V and timings are like 19-19-19-39 or like that (so default JEDEC profile i assume). But the problem with double boot is still there.
So i google "RAM training" and thats what i learned. If i try to run my RAM without any XMP profile it should start with 2400Mhz and 1.2V. And there is a thing called "RAM training voltage". So without any XMP profile enabled training voltage is set by default to 1.2V. And my PC trying to boot my RAM at 1.2V. But it seem like its failing, and thats what causes reboot. Then its trying to boot at higher voltage and finds out that 1.224V is good enough to boot RAM at 2400Mhz and just boots the system.
So the same thing happens when i trying to boot my PC with XMP profile enabled. But instead of getting default training voltage which is 1.2V it gets voltage of XMP profile which is 1.35V. And then the same thing happening. Its trying to boot at 1.35V but failing and then boots at 1.38V.
The only thing confronting with this theory is when i manually put 1.38V in my DRAM voltage and the system boot my RAM at 1.4V. It doesn't make any sense.
Please correct me if i am wrong.
Another wierd thing is that shortly after i turned my PC off (like 20-30 seconds), i turn it on again and i dont get my mobo start twice.