Can’t Log-Off

When I go to “Log Off”,or enter the command to shut down…My computer starts a normal shut down process.It
then, right when it would normally close, a screen pops up! This screen
states that my pc has malfunctioned
and it is saving this and that.Then
before I can read anymore of it,it
goes dead for a few secs then it starts a new start up.Just as if I
had started it from scratch…
Can anybody help?