The windmilling is just beginning at this moment. But Increase the forward speed to 30 m/s and the engine will be driven by the propeller at say 2600 rpm (propeller at 1000 rpm). Then the representative blade element will have a circumferential speed of 65 m/s. Its angle of attack would be zero for a pitch of : Atan (30/65) = 25 degrees. This is about 5 degrees more than the pitch angle (Hence CL = - 0.5 ) and the propeller pull would then be about -350 N.
Such an increase in drag would be very noticeable
For simplicity, I have neglected the induced speed
Windmilling does not mean restarting the engine. It just means aerodynamic torque helping it rotation.
To restart the engine, a greater aerodynamic torque is needed to overcome the first compression.
Only then it can continue to run without any explosion