Blinking underscore problem

[frgchsr]

Hello everyone, weird problem appeared two days ago. I bought Sandisk SSD Plus 240 and I installed Windows 10 using USB with Media Creation Tool. Installation went smooth, and then I deceided to restart my PC. My computer showed blinking underscore in top left corner for 7-10 seconds, then BIOS screen and then another blinking underscore (but very short this time) and it booted to desktop. Whole process was around 20 seconds long. What could be problem?

PC specs:
Ryzen 5 1600
G.Skill V Ripjaws 16GB 3200Mhz
MSI B350M Mortar (newest BIOS)
Sandisk SSD Plus 240gb + WD 1TB (disconnected at the time of windows installation)
660Ti
Seasonic M12 EVO 550w

Boot order is set to UEFI Windows Boot Manager Sandisk SSD Plus.

 

[hang-the-9]

Go into the BIOS, make sure the new SSD disk is first in the boot sequence, see how that works.

 

[frgchsr]

Go into the BIOS, make sure the new SSD disk is first in the boot sequence, see how that works.

Hi, thanks for the reply!

I solved my problem and below I will explain how.
As said above my motherboard is MSI B350M Mortar with newest bios and that was the problem.
For some reason, newest version has some sort of bug which makes my boot time very slow.
As solution, I flashed older bios with the help of the MSI tool (not M-Flash) that I found on MSI forum (M-Flash isn't working when you have newer bios than one that you want to flash - in my case older one).
I'm writing this on phone and I will update my post as soon as I get home.
Sorry for bad English