My 96 Van was doing the exact same thing. I had the van in to do some work prior to setting it up to tow a trailer when it was discovered the engine mounts and transmission mounts were nearly tore apart. The engine was just resting on them. I never gave it any thought until a few days after they were replaced that it stopped stalling when I put it in gear. Hope it helps.
Check the air filter to see if it is stopped up. Check all the vacuum hoses for a leak. Replace the PCV valve.
Dirt in the carb, Dirty plugged up fuel filter, Dirty plugged up air filter,
My 1998 E320 did this. Dealer charged me $1,100 for the fuel pump and filter.
My 1998 E320 did this and it was the fuel pump. The dealer also replaced the filter and it was $1,100.
Probably an alternator.
Impossible to say but I'd check/replace the fuel filter. It's cheap to do and if it doesn't help you've lost nothing.
Check the fuel filter. If it is the original, change it. If that doesn't help, find a mechanic.
change fuel filter
Partially clogged fuel filter or weak fuel pump. Replace the fuel filter.
Dirty injectors.
It sounds like it could be an ignition module. Take it off and take it to Oreilly's or a parts store that can test it. It is the fuel filter inline by the engine,replace filter and it will run fine.
It sounds like your alternator is no longer recharging your battery. You probably need a new alternator.