This could happen for A number of reasons. The 2 most common are “no air flow” on the bottom when in use. Make sure when you use your Chromebook, you have good “air flow” under it, on a hard flat surface is the best. Don't keep it sitting on A pillow, mattress, blankets, ect. this blocks the air flow under the Chromebook. The 2nd reason, A bad fan. All Chromebooks don't have fans, but for the books that do, fans get full of dust, loose exc. over time. Also checking the bottom of the Chromebook making sure the wholes are not full of dust is a good start.

i think your right, Needs A mother bord or has hard drive issue. I would guess mother bord.