plugs will only set you back £10 I would imagine so start there, you could always feel the leads when the car is running, see if you get a shock might make you jump a bit.

When you change the plugs (easy job) look at the ends, are they a light brown colour, if so the engines in ok condition, any other colour ask on here and we'll tell you what it means.

If it persists after this, change the leads. Really should keep the engine serviced and looked after, no good having a tidy little motor with tasty little mods if it's stuck on the drive.

Let us know how you get on