Hi donna another italian here
. Ok I owned a 300E for yrs. Donna if your dont drive it much. I recomend a battery cut off switch. This will keep the life of ther battery. Or a trickle charger ,this will keep the battery charged all the time. I works out great if you own a garage,and can plug it in when you get home. So it says nicely charge over night. If your not into getting under the hood, you can have your local mechanic install one,or the battry cutoff switch you can buy it at any pepboys or local parts store. As all the other guys mention. Those
over voltage protection relays,can play with the cars brain and do some funny things.
hope this helps goodluck.
Factory MB tech 14 yrs