How come my computer beeps 3 times and only shows me my Dell logo?

Q: I have a dell computer and this has happened three times to us now. the first to time i was able to fix it by unplugging the main cord and letting it sit for a hour or so. but now we have the same issue where the computer is on but it only shows the “dell” logo then beeps 3 times and show a blank screen. we have done the same process as before but its not working.