mine did the same for a while Its an '09 Thai built d40. Prone to stalling at the lights etc & then had to have a minute before it would run.Change the fuel filter if you haven't recently, dose it up with fuel/tank cleaner to get rid of water & algae in the tank & if that doesn't do it try a new suction control valve. They are all things you can do yourself, tho the scv is a bit of a pain to get at. I like to pump the fuel thru & fill the outlet hose from the f/filter before I connect it finally too...just to keep air out of the system.
Works for me anyway.
Good luck
Pete