300SE Auto Erratic idling & cut out

[Jansails47]

Hi, I'm pulling my hair out with my 1992 300SE. Bear in mind that I don't do technical talk and am simply trying to get a garage to sort this problem. Over the last few months, whilst in traffic, or at lights, and ticking over the engine has stalled, prior to this happening, the revs go up & down several times and then it cuts out. It always (up until now) starts again though. Recently having stopped to fill up with fuel, the engine took some time to start. Having just given the car to yet another garage they report they can't find anything wrong with the car!

I have looked at other threads and see some similar problems, although they don't seem to be associated with the engine actually cutting out. Any ideas?

Thanks