Ive never had a successful WILD during an afternoon nap but the experience i gained was invalueable. When i first started i would get to imagery then become excited and wake my self up with thoughts. Then about a week after attempting them every day i got to the transition feeling which i thought was hypnic jerk but it was the transition feeling i get during my WILDs without a REM cycle to fall into. The technique i refined during afternoon naps is the same i use during WBTB and the practice gained during make for a quick learning curve.

This is just my experience with them i do not know if this is normal but i just wanted to add my experiences in hope it may help you. Good luck!