iMac Won't Stay Asleep

My iMac will not stay asleep, despite me putting it in sleep mode manually or it sleeping automatically after ten minutes. The screen will be off for several seconds up to a minute and then wake back up. I restored the Energy Saver defaults in an attempt to fix it. The problem occurred yesterday, but I never had this problem before. I had not made any changes to settings or my computer before this problem occurred. Any help would be greatly appreciated. Let me know if anyone needs any more information!