This may be due to the motor being strained as it attempts to accelerate the bike and rider from a dead stop. If excessive weight is on the front wheel the motor may be applying an excessive amount of torque causing vibrations in the fork or a jerky behaviour.
Possible solutions to this include:
- Lean back slightly to distribute more weight to the back wheel, reducing the weight on the front wheel.
- Input more pedalling power in order to alleviate the work the motor needs to put in on start, downshifting gear as well may prove effective.
- Slowly pedal from start to give ample time for the motor to reach cruise speed.