> or even shocked (as if I appeared from thin air)
Motorcyclists are invisible. Never rely on others seeing you, ride as if they're an obstacle you have to navigate.
You can hide a whole truck behind the A-pillar of modern cars, let alone a motorcycle. At certain angles, human eyes have complete blind spots that we're not aware of because our brain filters them out. Motorcycles fit perfectly into those.
Never hover in people's blind spots. Pass quickly or stay back. Do not drive parallel with another vehicle. Goes for cars too.
When approaching another car perpendicularly (like an intersection), remember that humans lose depth perception because their nose covers one of the eyes. A driver literally cannot tell how far you are. Our usual proxy is the distance between headlights. Motorcyles have 1 headlight so this heuristic doesn't work, but we don't realize that it doesn't.
https://www.youtube.com/watch?v=x94PGgYKHQ0