I had a problem with my Dell, sounds like the same thing. I noticed Microsoft Silverlight had loaded itself on...I removed it and it is fine now. Someone else on a forum had a similar problem and it was a program named DropBox that was causing it.
Possibly check for any newly loaded programs you didn’t load.
Several have already said it, HEAT...
Same for desktops or laptops, heat is always an issue, especially if you don’t clean out the dust bunnies now and then.
Dust acts as a blanket and holds heat in, it also blocks the air intake ports, so the fan can’t cool the CPU well.
Check the link someone else already posted, here it is again
http://www.myfixguide.com/manual/dell-latitude-e6540-disassembly/
Check the air intake, you’ll probably see dust there, first thing to do is clean it out.
Malware will not often cause sudden shut downs, if it just suddenly shuts off and you get the bad shutdown message, it means it shut down without going through the normal shutdown process, which can cause problems.
Check for heat problems first, then look at other possibilities.