I'd bet that the piggy back red wire at the battery neg terminal is loose and/or
has a crappy terminal (Corroded at the crimp and resistive) If the piggy back wire
is off, you also lose battery charging, does your battery stay charged?
The ignition switch is in series with this stuff as the other guy posted

Also service your battery cable ends. look at where the cables are crimped on the terminal ends. Those connections can get bad. There's a pair of neg cables to the frame. take that stuff off wire brush it, grease it with neverseez and bolt it up. service the grounds at the intake manifold and firewall. They're critical
for the fuel injection.

Bill