Q: Macbook Pro beeping 3 times every 5 seconds

My Macbook Pro starting beeping after I put it in Sleep Mode. I had to force power it off. This has been occurring for over a month on a weekly basis, but this time I can't solve the problem. I already tried resetting the PRAM and the SCM. I ran the diagnostic test a few weeks back and it came back that nothing is wrong. I don't know if it is important to add, but I've been having trouble with the fan running/overheating, burn out spots on the screen, and a weird green and black glitch that causes it to freeze up.