Seems to me you need a new wheel speed sensor. I believe the back left is the one for the speedo. You need to scan the car abs module and find the code and it will tell you what sensor is faulty.
Also check your battery/charging system. A weak battery can cause many random odd faults
2008 e92 335i 6 speed, Intake
2005 Sea Doo RXT (stock for now....)
2004 545i 6 speed, lots of mods- SOLD