Well, I though about filing a bug, so that developers could look into it – if it’s some mistake in Fedora itself (or in some of packages/programs used in Fedora). But after some more websearch it looks like BIOS/UEFI problem (as @xtym and @vgaetera already pointed), and I see reports about same problem with Ubuntu and maybe some other distributions too.
Can you please check this – second – answer (and third too):
The first answer is basically the same as what @xtym suggested from the start, but here Xeno talks about HP notebook specifically. Please see if you have an option he talks about in your BIOS/UEFI settings.
After partially reading / partially looking through rather long bug @xtym pointed to and several other questions/answers about your problem I think that maybe it’ll be easier to just reinstall Fedora in legacy/BIOS (not UEFI mode).
There are some other hacks you can try (several are detailed through the RHBZ bug 1512410) – but they (1) may work or not work and (2) may need constant manual actions to maintain – after every kernel update, for example – so would be not very convenient in the long run.
From what I’ve read – and it’s largely a guess on my part, I didn’t find it written clearly – though Yves L’ECUYER did quite detailed testing you can see in the comments to the RHBZ bugreport – one reason for this behavior may be the UEFI of your notebook don’t want to boot Fedora’s /EFI/fedora/shimx64.efi file and instead boots /EFI/BOOT/BOOTX64.efi – which could be (not sure here too) a fallback bootloader, which keeps displaying the message you’ve reported and adding Fedora’s boot entries – which UEFI then again ignores.
Workarounds @xtym suggested and Xeno written for HP in the askubuntu link I’ve posted rectify this behavior on the UEFI’s part.
And it doesn’t look like something we can change from inside the Fedora.