I had the same happen to mine - what fuel you using ? Have u changed lately ??
I ended up changing the MAF / Coil / Dizzy / Rotor ar and cap / cleaning the throttlebody / changing pipework / new ignition amp and still it was their although a lot better - I used one tank of BP ultimate around the time, went back to Optimax and no problem ??
It's been as good as gold since, but I have only used optimax (I always do too other than that one tank in 2 years now !)