Hi ,
I'm Dyari. Thanks for reaching out. I will be happy to assist you in this regard.
Pressing Shift with shutdown usually fully shuts down the computer not directly reset the Windows to the factory settings.
Have you reset your Windows? if not and you see your computer is slow, please turn off the computer completely (not restart or pressing shift) and then turn it on. Does it function properly?
There are also some tips to follow to improve your computer's performance:
https://support.microsoft.com/en-us/windows/tip...
Please let me know if you need further assistance.