I think we'd most guess Gpu overheating, happens very often in notebooks. Also beware of malware that uses your Gpu to mine bitcoins, it'll push your Gpu to 99-100% usage, use windows malware removal tool. In search I think it's just 'MRT'. It'll update and scan, these malwares are notorious, especially for people who torrent games.... Makes sense...
Anyway if you have more problems, try that, and also post alll of your specifications, hardware, OS, anti-malware/anti-virus, etc. No such thing as too much info. GL
-David