Mercades 280SE Auto (W126)

Hi Guys,
I've got a Merc 280SE with very few miles on the clock (61k) and it is behaving very strangely lately. In fact I had to drive my girlfriends
Clio to work most of this week until I can get time to sort it. I wonder if anyone here can diagnose my problem as I need to collect some people from the airport on Sunday and the Clio will get a bit cramped.
When I start in the morning it is fine, then I get about a mile and the engine won't give me more than a modest amount of power 1700 rpm, even if I kick down it stays the same steady pace. Then it really doesn't like going up hill. When I stop at in traffic or at lights it might (or might not) die, although if I put it in neutral it probably won't stall and even less likely if I keep my foot touching the accelerator (gas). Pulling away I have a small chance of dying as well.
Then, what made me put the car down was that I was driving away from lights at about 20-25mph (about all it will give me) and trying to accelerate, I thought I realised I was giving a fair bit of smoke. I took it home and swapped it for the Clio.
Today I drove in and the car was fine for the first 8miles, but then just failed on me in traffic (on a bridge no less) and from then on it was really difficult to keep it alive if I stopped. At one point I heard the sound of snagged blades spinning down as it died (I thought that was the end of the car). But it restarted after some key turning.
Just now in the car-park at work I thought I would see if I could see anything wrong, it was fine, but then I rev'ed the engine up modestly high then let it fall first this was fine but I noticed a rumble; then I rev'ed around a little looking for the rumble and then let it drop, it then died. After two attempts at this it would not restart, except after either the rest I gave it or the fact that I thought to try rolling it forward a little to change the engine mechanical positions. It then restarted fine, however I could now repeat the rev-up and die easily.
Current suggestions include: Transmission fluid/impeller. Ignition system: rotor arm / distributor cap / spark plugs / ignition leads Fuel pump Air flow sensor
But nothing conclusive, I can't find a mechanic who can see it before Monday, and in fact I will be brave driving home. Can anyone give me a clue?
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