Vibration. (More than usual!!)

My '06 GRiSO has been running sweetly for a good while now.
Riding home from work the other night, the bike felt just wrong, but I was unable to work out what. I thought maybe I was imagining things.
After a long 200 mile ride today, my hands and arms were tingling which has never happened before, and I'm sure there's a high frequency vibration from the engine.
It's definitely running on both cylinders, but I'm wondering if there's an intermittent ignition fault. Inner and outer sparkplugs were replaced about 5,000 miles ago but the plug caps and HT leads are the originals.
I don't tend to play around with the bike when it's running well, (I'm "if it ain't broke, don't fix it" owner) so I've not touched the throttle bodies, stepper or anything like that. I loaded a Beetlemap about 5 years ago, which is the last time it was hooked up to GuzziDiag.
So, the big question is, can anybody offer some words of advice please?
Thanks.

I'd check things known to cause vibration first....Broken Pretzel and/or loose exhaust bracket....also worth checking engine mounting bolts are still tight.

After checking the things that Paul says,

If it still buzzes: look at loose things that can buzz: exhaust shield, headers, footrest bolts - in fact tighten everything

If it still buzzes: resynch the throttles.

If it still buzzes: check the airbox for oil (through the inspection window) - you may have to clean the throttle bodies and air bleed