Mobile homes are manufactured on a towable steel framework, which makes for easy transportation to their permanent location.  The standard for mobile home foundation installation is hollow CMU block with a concrete pad and wood shims.  These piers sit on the surface soil layer, which is the most susceptible to shifting.  Wood shims compress over time, which also contributes to a shifting mobile home foundation.  You may experience a sloped or humped appearance to floors, cracks in walls, or doors or windows that no longer open/close properly.  These are all signs that you need a mobile home foundation repair.