My bike has developed an intermittent problem. If you jump on the bike after it's been sitting a while, kick up the side-stand, turn on the ignition, pull in the clutch and push the starter every now and again nothing happens. If you do something, like release the clutch, turn the bars slightly and try it again it fires up first push... It doesn't seem to always happen, but it has done it four times this week. It also doesn't happen first thing in the morning when it's bloody cold and the bike has been sitting in the shed all night.
I'm wondering if it's the first sign of the battery going and the first push or two of the starter gets things moving internally within the cells just enough to kick her over...although when it does fire up it sounds fine. I'm pretty sure the battery is the original, so it's been in the bike since '98, I've had her 2 and a half years, done 40,000km, and I haven't touched it. I'm presuming they don't last forever, but what are the symptoms when they start to fail? Bike just won't kick over at all/sluggish kick over???
It could also be dirty contacts within the starter switch, problem in the clutch switch/side stand switch/starter motor, but where do you start?
I'm also presuming I'm not the first time someone has experienced something like this, surely one of you guys/girls has the answer...

Any info welcome.
Thanks