I have a SLK320 2004 that have been having problems. The issues i have are:

1) rough idle sometimes the engine just dies, restarts straight away
2) Engine dies at speed, coasts to a stop turn ignition and nothing, wait a few mins turn ignition and the engine cranks and starts fine.
3) Engine dies at speed, take foot off gas for a few seconds and it fires back up and continues down the road accelerating again.

sometimes this happens consecutive days sometimes it doesnt happen for weeks.

Oh and no check engine light or anything else.

Im out of Full warranty and dont relish the thought of it sitting in a dealer for weeks at charge.

If anyone has had the same problems with resolution i'd be very interested to hear how they were fixed. At least this may give the dealer some idea of what the problem is. Thanks.

Seems to me that this may be relatively easy to isolate, I believe it would safe to assume that this is probably an electrical matter.

Questions I might ask you

1) Do any warning lights flash or illuminate prior to the engine dieing?
2) Are there any other odd or unusual electrical issues?

Questions I might ask myself as the technician

1) How is the fuel pump powered up?
3) How is the fuel injection system powered up?
4) How can I duplicate the complaint?

Based on your complaint my immediate suspicions would direct my attention toward the K40 relay assembly. I would perform a number of voltage drop tests through the controlled circuits to see if I have an underlying problem with the contacts. Relay contacts can be a source of unwanted resistance in a circuit because when they close they arc. When the contacts arc numerous times (hundreds/thousands) they eventually burn, this eventually develops unwanted resistance in a circuit.
(High Resistance = Low current)

Just my .02 at 0 coffee hundred, at 0 beer 30 my .02 is for the cold one……………….

Thanks, i had narrowed it down to the fuel pump/relay after reading posts here an elsewhere. However, one thing that concerns me is that when the engine dies and i stop i turn off the ignition, turn it on (all lights come on dash as normal) but when i turn the key nothing happens, no click no turn of the engine nothing. After i wait a few mins and try again all is well and it starts up like nothing was wrong.

also, no lights are illuminated both Prior and after the engine dies.

Thanks again

You may also want to double check your battrery connections, you just never know what you will find when cover the basiscs one more time!