mattress-magnetism
A strong/intense EMF-field that emanates from your bed-springs; said powerful field creates a debilitating "pull" on the iron in your blood and thus makes it very hard for you to get out of bed, especially on those occasions when it is absolutely necessary for you to do so, such as when it's time to get ready for work, you "need to pee real bad", the telephone or doorbell rings, someone else in the household (child, pet, elderly house-guest, etc.) urgently requires your assistance, etc.
I am firmly convinced dat there is a great conspiracy among Sealy, Serta, and da other major mattress-manufacturers to intentionally create mattresses that mess with your body and cause you to feel groggy and heavy when trying to lift your head up off da pillow. Perhaps they specifically design their mattresses' coil-springs to act like magnetic coils that harness the earth's magnetic field and then create a strong magnetic pull on your iron-rich blood, this "mattress-magnetism" is why it's often such a gargantuan struggle to raise yerself off da sheets.