Laptop doesn't shut down fully when auto shutoff done.

I bought a Toshiba laptop a couple of years ago, it was shutting fine until the other day, my husband was turning on the machine and he noticed the screen said "Windows did not shut down correctly". Will start up in 15 seconds. I am very concerned that if the machine is getting a virus or just malfunctioning. I had the computer serviced last year because it had crashed. Glad I had a warrantee on it. What should I do now to fix the "shutting down/ windows not shutting down properly issue? Can anyone help me please?