iMac shuts off after coming out of sleep mode

I've noticed recently that my 2011 iMac has been restarting by itself as soon as it comes out of sleep mode. Sometimes it restarts once and sometimes it'll do it all over again. I have no idea why it's doing this and I'm getting worried.

Can anyone help?

Also, I'm running Mavericks 10.9.5. I can provide any other info that is needed if it can help fix my problem. Thanks!