Mattresses sometimes slide around on platform beds if the mattress is too big or too small for the frame or the bed frame lacks side panels to keep it in place. If the mattress is too big—for example, if you use a king on top of a queen platform bed—your mattress may droop off the sides, feel unsupported, and shift around. If your mattress is too small, there will be room for your mattress to move around on the frame. If you do experience a lot of movement, first make sure your mattress and frame are the correct sizes: queens on queens and kings on kings.
If your mattress is the correct size and you still wake up to a moving mattress, try adding nonslip pads to help keep it from wandering. These pads provide extra traction between your mattress and the frame to keep your mattress stay put while you sleep.