I did not mean to imply that this could ONLY be a fuel problem, just that the symptoms match well.
Certainly could be the relay.
You can jump terminals 7 & 8 at the relay connector, then feel the pump(s) to see if they operate.
The difficulty is that you would need to catch it in a failure state for this to be meaningful.
Is it starting now, or does it continue to be intermittent?
1986 300E 5-Speed 240k mi.