M-B C220 power loss uphill

I’ve got a 1994 Mercedes C220 which recently has been losing power going uphill. This is a random occurrence but starting to happen more frequently. When going up a hill the car engine starts to “miss” and the engine sounds like its fluttering. It is definitely losing power.
When I get to the top of the hill; if I turn the engine off and restart it all goes back to normal and runs properly.
what is it?
Thanks

Start with a compression check.
From there, if that’s good (don;t get optimistic), test the fuel pump.
Post back with the results.

The problem might be with the catalytic converters becoming restricted.

Your vehicle has the OBDI engine management system. So the catalytic converter effiency isn’t monitored as it is with the OBDII engine management system. So the cats can become restricted where the engine loses power under a load but the Check Engine light doesn’t come on.

Tester