Old mercedes

I bought a 1991 SEL 300 Mercedes for my 18 yr old daughter to drive. It has around 1900000 and I love driving it. (She does too, I’m happy to add.) And it ran really well until a month ago. Now when I start it, it runs well for ca. 3 minutes once I get going, but then it stalls out, and it won’t start again. It sounds as if the engine is not getting gas, or the gas is not getting a spark. I replaced the spark plug wires, at one mechanics suggestion, who said they were sparking and old. But this didn’t work. Another mechanic has told me that the car might need an ignition coil, but this could cost up to $2000 to install. Furthermore, ,the mechanic is not sure that this is the problem. The car is only worth ca $3000. I’d love to keep it. Does anyone know what is wrong with it? Or how it can be repaired for less money? Thanks!

Note, duplicate thread … See replies in the other thread.

Which other thread? Where?

Oh, wait, I am not sure where it is, but I found it by clicking on the user i.d. and it showed both of them. so at least I was able to read the excellent answer.