Problem at srart then back to normal

Toyota Sienna 2013 . Clicking sound ( like a torn belt slapping ) after starting.
Turned it off a d then tried to restart. Engine cranked - lots of whining sound -  
but car did not start. I guessed it would be a fuel pump or injector problem so
got back in to check the net.
Half an hour later, I tried restarting again  and it did start & drives well.
What should I look into as a precaution. This was the first problem I ever had
with this car. I would have said it was a stuck fuel pump or a blockage in the
fuel filter had there not been the slapping sound when I first started. It was a lot
louder than a typjcal cold start / valve tapping sound