when ever i go to watch videos on youtube or any other apps, the screen goes black. you can hear the video but you cant see anything. how do i fix this?

i have an ipod tough 3g and its like about 4 to 5 years old it works perfectly fine except the home button is abit messed up and the ipod sometimes crashes. but other than that everything is fine. so i was watching something on an app and then al of a sudden i dont see the video i can just hear it. i then think its just the app but when i go on youtube the same exact thing happens. you click to watch a video and you can hear it perfectly but you cant see anything. the screen is just black when u ONLY watch a video. this happened last night so yea.i really hope somebody can help me figure out how to fix this and whats wrongwith it:)

thanks for your time and help!

Noor .T.🙂😍😀