The doors hinges have grease fittings but take a special type of needle type injector for the grease.
The door check was redesigned just before your car was made and the new design is about impossible to lube from the outside. It uses two balls that retract back into the same tube which is verticle and inside the check itself. We use a product made by Wurth called HHS. It is originally about the consistancy of WD40 which can creap into and up through surface tension. After about a minute it thickens to a coating almost as thick as wheel bearing grease.
The problem is hopefully in the door check as an abused hinge is hard to repair.
Bosch Master, ASE Master, L1
33 years MB technician