starting issues after car sits for a while

[CrisZenithBlue]

hi guys,

2000 base boxster, 140k miles on the clock. never failed to start since i got it 3 years ago. recently refurbished all injectors and mechanic had to remove the intake to get to the ones on the air box side.

car starts first crank in the morning. once i shut the engine off and i come a few hours later it struggles to start as if it's not getting gas. acts similarly to when you run out of gas and you have to crank it for a few seconds until gas reaches the engine after refill. it typically starts after 3-4 seconds of cranking, most of the time depending how long it was since it ran when i return to the car. in the morning it starts perfectly.

is all the gas going back to the tank somehow?
mechanic did mention he noticed my gas pump was loose in the tank and he tightened it down. did he mess something up?

where should i look first?

thanks,

Cristian