I've had this laptop for about 3-4 years now (And even though I'm getting it replaced at Christmas this problem is still really annoying) and it's started to run into a problem were I could be doing anything from playing a game to searching the web were my system will suddenly just start going incredibly sluggish and turn into a un-usable mess. The mouse moves but I'm not able to actually do anything cause it's pretty much like the laptop has actually crashed. The only solution is to turn the whole machine off via the power button and wait for it to load back up again. This problem didn't used to be too bad as it happened every few days but now it seems to be happening every hour or two and I really need a solution! Any help here?
Firstly, do you have a backup of your important files? It sounds like it could be a failing hard drive. Have a look at the event viewer in admin tools. Under windows logs and system. Look for any ntfs or disk errors.
Couple years ago, Lenovo went through a recall where their battery was subject to replacement because of possible failure prematurely. Have you tried testing your laptop by taking out the battery and plugging it in? Check for errors that way and if it does, your battery pack could be the problem. How do I know? I have a Lenovo y510p and you should have been contacted by the manufacturer for a free replacement (in 2014'ish). Good luck!