I would tend to lean away
from a fueling problem if you pardon the pun.
A bad earthing point?....
The simplest solution: Is your battery insecure and moving and loosing the negative contact?
Fuel pump relay, is it making good contact on its connections?
Remove the battery, make good all the earthing points to the body and ECU, check the connections to the relays, clean them up and inspect the underside of the relay connections underneath, chances are they will be corroded somewhat , refit it all back in place and see if that rectifies the issue
, just an hour of your time maximum and the knowledge that you have eliminated any future worries from that area.
If that still hasnt rectified the problem, then move onto underneath the engine cover, check and clean the fuel rail/injector electrical connections. If they are ok then move onto the next logical step
Lift the rear bench seat and inspect the connections to the fuel pump through the inspection cover, they could have worked loose slightly.