In all honesty, it might just be a software thing. I've been careful making sure I close my apps rather than leaving them running in the background, having a lot running could be your cause? Other than that, id say just restore your firmware on your surface. Trust me, its not as bad as you'd think, Microsoft makes it real easy to get all your stuff back, just have documents backed up on a flash drive just in case!
Edit: Now that I think about it, the surface I got that problem on was my old surface... im using a new one now. Could still be software tho, try a restore