Here's the final form of my project.
I've added motor detach function since it still shivers a bit.
const int MPU_addr=0x68; // MPU-6050 I2C address
SoftwareSerial BTSerial(3, 2); // TX, RX
const byte pinMini = 6;
I think you want something like Blink Without Delay, but with more tasks.
Here is my interpretation of your description which extends Blink Without Delay by adding three more tasks to:
read the accelerometer
perform "just once"
perform "also just once"
I've added several Serial.print() statements to give a running commentary on what's ...