Unexpected shutdown when not charging

I have come across an issue with my laptop today,it is a toshiba satellite and it is more than 3 years old.

I unplugged it earlier today and after a couple of minutes,it shut down instantly;no blue screens,no error messages,much like a pc shuts down when unplugged.

After that,i plugged it back in and carried on with my stuff.However,i tried to uplug it again and the exact same thing happened;twice actually.

What do you think?Should i get it cleaned?Should i buy a new battery?

Cheers