If you're using the original battery, replace it.
Check the starter button. If it's not making proper contact or the wiring to it is compromised, there's your problem.
Does the headlight turn off when you press the starter button? If not, try replacing the starter relay.
Check continuity in the clutch switch and especially the side stand switch. Is the neutral light on?
2005 Bonneville Blue 790cc, AI removed, Staintunes RC, Uni filter, no snorkel, 118/40/NBZT "Thruxton" needles/1 shim/3 turns, tachometer, Ikon 7610s, Ricor Intiminators, Dunlop GT501s, D9 gauge panel.