Peugeot Speedfight 100cc Front Steering Shakes?

My Peugeot Speedfight 100cc has just started shaking in the front end and I'm searching for ideas as to why? I first noticed it when I was carrying a passenger and I just thought it was the extra weight. It did it again today with just me onboard so its definately not the passenger. The handlebars start wobbling almost like speedwobbles however it also happens at slow speeds around 20-30mph, and especially if I take one hand off the bars. I'm running 26-28psi in both the front and rear tyres.....any ideas anyone??