I don't think so that is fuel pump check valve problem because i replaced a brand new Bosch fuel pump about 2 years ago. I parked the car over a year. Before park the car, it can start anytime perfect.

Yesterday, I refill the premium chervon gas in that car. Since improved on starting. At least, I can feel that little easy on starting. I will keep update in next few days. Hopefully, it causes by poor quality gas. Not something wrong on the car.