BMW E61 servotronic driving control system, ABS, tire pressure sensor failed, check battery contacts? Troubleshooting 520d?

Hello, I don't know what's wrong with the car. It's very irregular that this series of errors occurs. Sometimes it happens about every 20 seconds (the speedometer goes off completely and then back on again). Afterwards, one or more of the failure displays come on at irregular intervals. Sometimes it's when I'm driving uphill, sometimes…