The simplest fix would be failed or misseated memory. Remove the memory cover and then try this:
1) Remove, and then re-seat the memory.
3) Remove, and then re-seat the memory in the other memory slot.
5) Try replacing the RAM or testing the old RAM in another notebook.
Since the battery meter shows a full charge, we can assume for the time being that the battery and AC adapter are not at fault. That leaves not-so-easy-to-fix components like a failed CPU or motherboard. I suppose it's possible that it could be a failed fan (system detects 0RPM and shuts down to prevent overheating), but that's unlikely.
Let's hope that it's something simple like the RAM.