Do the "electrical" get dim when you go to the starter position on the key?
Have you looked at the battery terminals to check for tightness and corrosion?
Did you turn on the headlights and are they bright?
Do the lights dim when you try and start the car?
How old is the battery?

I would check these first before you start jumping things.

__________________
1991 300 SEL
218,000 Km

"Xsbank's rules of mechanical intervention: Always go for the easiest solution first; 90% of what ails a gasoline engine is ignition; After that its all a WAG."