Roujin Z (1991) IMDb
Ōtomo Katsuhiro (writer).
An artificially intelligent all-inclusive bed can take care of the growing problem of elderly Japanese needing constant attention. Unfortunately, the AI is supplied by the American military for clandestine field testing, which turns the bed into a rampaging mecha that impersonates the dead wife of its aged patient, conquering all on the way to the ocean at Kamakura.
A simple and good idea for SF with some social commentary, embellished with an hour of ridiculous action. Nice ending.
References here: Stink Bomb (1996).