[SOLVED] PC can't find the os

[Mlado53]

After adding another gpu(nvidia gtx) the system cant find the os(same after removing it).
It recognizes it in the bios. After turning CMS off it turns it self on after getting in to the bios again.
After getting a windows 10 USB I did a system restore that got me in to the os again but the next day it happened again.
Tried to do a sys restore again but now it doesn't know that there was an os.
What can i do.

System:
R5 2600x
rx 580
8GB ram
850W psu
500GB intel p660 ssd (OS)
500GB hdd
B450 Motherboard
Windows 10

Edit:
Fix: After moving the ram for the second time it booted.

 

[Yukoncorny]

Instead of a system restore can you do a fresh install of Windows?