What cause bodily movements within society after demise?

What causes bodily movements(ie collar moving back and forth, finger or leg movement) after someone dies?What cause bodily movements within society after demise?
Spirit trying to find out of the dead body.
The bodily movements are just observed in cases where on earth body tries to hold on to the spirit. This happens when a soul who was not within peace with his or her spirit during the energy time makes a desperate attempt at the later minute to contain the spirit. Spirit has wing and is stronger so it shakes the body violently contained by an attempt to reject the body's wish....which is not to die.
Rigor mortis
nerves
capricious electrical impulses within the nervous system.
Reflexes and rigor mortis
u connote a few sec. after death --I've see this and they tell me it's refexes that are surrounded by the process of death but a spontaneous effect will occur sometimes for 2 to 3 second from nerve impulse.

rodents