How can I fix my original Surface Pro?

[LP Slade]

I have the original Surface Pro and I haven't really used it for a while because it was so slow. I tried to use it tonight and although it has a full battery and is plugged in, the screen keeps turning off after every few seconds. Is it just too old? Or can I somehow reset it (even though every few seconds the screen turns off??)? I have Windows 10 installed.