Camera beeps but won't turn on

Hello, when I try to turn on my camera, the power button turns green, beeps around 4 times, and just never turns on. Screen stays black the whole time. I have a fully charged battery in it. I did try inserting an SD card I had on hand, but I didn't know if it required one to even turn on. I don't really want to go through the effort of buying one if it still won't turn on.

Things to note: I bought the camera itself off eBay and haven't tried to clean it or anything yet. Any help would be appreciated, thanks!