All of the cities in your itinerary are major tourist stops, so no real issues for solo travelers. You may attract a little unwanted attention in Spain and Italy, but no real problems. Be firm if you want someone to leave you alone and don’t hesitate to raise enough of a fuss to attract attention if you feel uncomfortable. Sunglasses can help avoid eye contact that might be misinterpreted as a come-on.

I think you’d have a better time if you made some effort to get off the beaten tourist track and actually see and experience Europe. I would spend far more time in Eastern Europe and less time in the capital cities of Western Europe.

Thanks for the feedback. I will definitely look into that!