Spróbuj z
import subprocess
import subprocess
SEKUNDY = '15'
subprocess.run(['shutdown', '/s', '/t', SEKUNDY], shell=True)
'''
lub
subprocess.run(['shutdown', '/s', '/t', SEKUNDY], shell=True, creationflags=subprocess.CREATE_NO_WINDOW)
'''
BTW, polecenie do usypiania kompa
import subprocess
subprocess.run(['rundll32.exe', 'powrprof.dll,SetSuspendState', '0,1,0'], shell=True)