Originally Posted by Vladamere

Heat is not the problem. I monitor temps, and my laptop behaves this way even when starting fresh and cold. Vents are cleaned regularly.

As far as tests..

Hard Drive SMART data reports 2 offline uncorrectable sectors (I don't think the Hard Drive would cause this) -- If you have run HDD diagnostics on the this HDD like Hitachi DFT then definitely this is hardware error. Consider HDD replacement. If you want, replace it temporarily so you will know.

Memtest= Pass

It's just so confusing.. -- please follow as advised and it would not be that confusing.