Latitude E6440 INACCESSIBLE_BOOT_DEVICE only when restarting

Hello! I have a Latitude E6440 installed with Win10 x64 Pro verison. I have the problem describet at subject: When I restarting my laptop, it gives me INACCESSIBLE_BOOT_DEVICE error. If I "choke" it to shutdown, then start it again or I shutdown it from Windows, then starting it again, it has no problem, Windows loads as usual. I changed the HDD to an ADAT SU650 240GB SSD. What csan cause this problem? I tried a lot of things found on Internet, but none of them solves my problem. Thanks for your reply!