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This is not an uncommon behavior and we need to locate the source of the problem and eliminate the things that are not effecting the issue.
Most probable causes:
Battery, Starter Relay, Start Button, Starter.
Manually start the bike and take it for a good rip and see if the battery takes/holds a good charge for the rest of the day. If you don't have trouble starting through out the day then it's a good chance you may need to replace the battery. Recommend the use of a trickle charger to keep the charge up during the week when bikes in the garage. Part# 53 Frame Parts/Wiring Harness.
If your battery is known to be new or has a good charge, do you often hear a clicking sound. It might indicate your starter relay is wearing out or you have a short. Trace the wire harness and confirm insulation wear.Check starter wire and confirm the nut's tight with a good star washer. If relay - replace it. Part Number #58 Frame/Wiring Harness
If the battery is known good and the relay pulls in but the starter won't engage and you can hear it attempting you may have an issue with the starter being in a bind from some internal obstruction or just plain worn out. Pull it and check it. See if it engages off the frame. You may have to take it to an alternator shop and have it re-wound. New ones are spendy.
Starter Control Button:
Reseat the connection and confirm it's engaging the relay.
Part Number #69 chassis/Handlebar Controls.
Hope this helps you resolve your starting issue. If we can provide further assistance please advise,