The doors stick because the latches no longer line up properly. Slight stresses on the body can cause doors to stick when attempting to open them... parking on an irregular or sloped surface etc.
To rectify... take an allen head wrench and loosen the two small bolts that hold the door latch to the post of the car(not the latch on the door itself but the one it latches onto).
Scribe a pencil line around the latch before loosening it. Then move the latch to new locations untill you find a spot that allows the door to open and close smoothly. Snug bolts each time you move latch to new location. Once you have the right adjustment ... tighten the bolts again. If you hear wind noise while driving after you are finished it means that you have the height adjusted correctly but the latch is adjusted too far out along the inward outward axis. The outside of the doors should be flush with the post.. when so, there should be no wind noise.
1993 190E 2.3
2000 Toyota 4x4 Tundra