A self-regulating damper unit comprising a cylinder having a first working chamber and a second working chamber, a piston, a piston rod, and a through-hole between the first working chamber and the second working chamber. The damper unit also comprises a shiftable weight which modifies a passage cross-section of the through-hole. The shiftable weight is movably mounted such that retardation of the piston causes enlargement of the passage cross-section. A seat belt unit comprises a seat belt and the damper unit.