So, the system suspends by itself?
Without you clicking on anything?
However, this is a desktop computer. I use it for more than four years. Is it possible?
I was talking about the rechargeable battery in a laptop. If it is nearly empty, the system suspend/hibernates automatically so you don’t loose your work suddenly because of power outage.
If the battery is old, it might not be possible to fully charge it any more, or it might loose power too fast. Or the charge state might be misdetected, but that’s unlikely if it only started to happen recently, I suppose.
I don’t know which battery I need to change?
On a desktop, none.