Seat belt tighten on bumpy road on 2008 altima.

A bad motor or cable what ever makes the seat recline . Viewing a repair manual an seeing what is broken is how to find the problem . https://www.nicoclub.com/FSM/Altima/2008/se.pdf

Seat belts are like air bad once they are activated in an accident they can not be reused. There is an explosive charge that tightens the belt

have the disc rotors checked for warpage and bad wear. Check that the wheel bearings are in good condition and properly adjusted. Check pad thickness as you may have metal on metal.

there is a gas charge that will tighten and lock the seat belt in a wreck and the seat belt will have to be replaced......sorry that i could not give you any good news.......let me and fixya know if i was able to answer your question and a comment and a thumbs up on how i did would be appreciated....thanks and good luck.......if i can help in any other way let me know........have a blessed day.......

dont cut the belt try to tighten more to release it or unbolt

you call it the serpentine belt, we call it the fanbelt.it,needs tightening,slightly loosen the alternator, then pull away from engine and tighten belt, tight enough when you can move longest part of the belt, between pulleys, 1/2 inch in/out.
if squeel re occurs fit new belt.

Are the sensors or connections dirty? I would clean them. You can also use a pliers and tighten the female end of sensor and place it back in the connector.

you will need to buy the female part of your seat belt.also you will need to pry the red push button out of the old one to get it apart.

could be broken timing belt or chain

take vehicle to the dealership, seat belts are lifetime warranty from 1987 on up, you get free working seat belts (dont mention accident at dealer).