Troubleshooting DC motor no load current with power supply
During startup there's no back EMF to limit the current, so your supply is likely going into current limit.  In general, motors need high current to get started.

Once the motor has started the back EMF "fights" the supply and the current drops.



eb is the back EMF in the equivalent circuit shown, and it's equal to the back EMF constant times the angular motor speed.  So at no load there's no eb to work against the source, and the current is only limited by the winding resistance Ra and the inductance La.

The reason for the voltage on your supply going to 2V is again the supply is hitting its current limit.  When you raise the current limit it allows the supply voltage to increase, increasing the motor speed.