I have a series of dumb questions
the obvious answer is buy a new battery, but just for the sake of argument if I am boosting the BMW battery from a second vehicle via jumper cables, and the starter doesn't turn over is there a way to hot wire the starter as well from the second vehicle? Just trying to get it running again its been sitting for two years, but was running and starting fine before I parked it. had it running last night and today its been frustrating?
Clean the battery cables...
sparkle clean. All 4 ends.
Then, pull the main and fuel injection relays and clean up the tabs...a disposable finger nail file works great. Spray electonic contact cleaner into the relay sockets.
Definitely clean the battery cables and at the
minimum pull the relays in and out a time or two to make sure they are in contact. Once running and with the battery charged you can spend the time to do all that Kevin said.