George,
My 93 400E aslo does the same thing and I find more so if I don't drive it for a few days. I have remote locking on mine and when I unlock it the plunger on the driver's door is slow and doesn't rise all the way. So I lock it again, and open it with the key and then get in, lock it with the remote and unlock it a second time and 'help' the plunger to rise. Does the trick every time. It did it so often I've disconnected the alarm horn which everyone now ignores anyway! Look for a sticking plunger in one of the doors,
check the vacuum lines to it or replace the plunger assy.

Tobias MB
4 MBs