Sticky latch? Might want to see if you can lube up the latch assembly. Probably just has junk in it.
open the door look where the post would meet the door, theres a latch there, with a screw driver pull on it while holding the door handle up. it will move so the slot there is now open and the door will close again.
do lube it up some.
easy right? what happens is that latch gets dry, you open the door and it flips back instead of open. it happens to all cars sooner or later. pretty much every car ive owned over the years, seems to happen more during winter time tho.