The only relay is the starter solenoid on the starter motor. Personally, I'd have the battery tested, especially since most auto parts stores will do it for free. If the battery terminal and cable connections are clean and tight, my bet is there's a problem with the battery. You need to establish a "known good baseline." This is part of that process. It's the first step in solving any automotive electrical problem.
The cause may be a bad alternator and the effects may be a discharged battery and a difficult to start engine. This link may help:
https://www.askmehelpdesk.com/cars-t...ml#post1973613
We know the starter motor and solenoid are likely fine--we don't know the condition of the battery and alternator.