First guess... heat. However, not enough info to have any confidence that this is the real issue.
Need specifics...lots of them- you are hands on, so....Video card? PSU? Monitor? Resolution spec selected in NFS game? DIY build or purchased from? When? Last time cleaned? Did you replace thermal paste? Have you tracked temperatures with a utility (HWInfo, Speccy, etc)? Last malware scan? Was it clean? Device Manager - any error conditions?
Detail issues leading up to crash. Messages? Error codes? Beep codes?