Can I jump start a 2000 s500 from under the hood? Steel key does not open trunk and there is no battery.

NO. But if you lift the carpet and floor panels in the passenger footwell area you can access the large battery cable that goes to the starter. Best thing to do is boost the battery there, but just open the trunk to access the battery. Then boost there to start the engine.

The same thing happened to my 2001 s500 I called Triple A and he hooked the cables to something under the hood of the car and it gave it enough juice for me to pop the trunk open and from there I was able to jump start the car

My question is this happen to me again right now so I'm trying to figure out do you know what the triple a guy hooked his jumper cables up to because I need access to my truck to jump start my car as I speak????