With regards to the starting fault, have you tried having the memory read on the ECU? If the injector light is flashing you might find there is a fault stored in the memory to point you in the right direction, but to be honest you should get an auto electrician or a competent mechanic to look at that as you might find it a complex fault to fix.
If the car is making clonking noises only since it was serviced.....take it back to where you had it done! If it sounds like it is behind you it might be a broken exhaust mount, have you had a look underneath? Although I agree with John145 about engine mounts! get a a friend to sit in the car with the engine running, hand brake on tight, you open the bonnet and look at the engine (stand to one side for the next bit, not in front of the car) get you friend to put the car in gear and let the clutch out gently and look to see if the engine moves much, it should move a small amount as it is mounted on rubber but if you are getting excessive movement you have a problem!
IF the engine is moving too much it could be stressing the wiring and causing your intermittent starting!!