My inexperienced input would be the ignition leads, my old Hyundai used to vbrate at low speeds, it was an auto, the stupid dealer could not fault it, then the problem went away, until one day it came back with a vengence, so I pulled out the ignition leads to see if the vibration would stop at idle, and guess what it did...
Being a manual it could be the clutch??? not sure never owned a manual car?
Clean the fuel lines out with an additive, change the spark pugs and it should be fine, As you say that you haven't driven the car for a while, so the system seems a little dried up, once it runs in it should smooth out, by fuel additives will prevent corrosion and contamination from settling.:thumb:
cud be a number of things if it is jumpin out of gear a gearbox problem or maybe a mount does the car wander across the road? wat are the other symptoms is it a petrol or diesel?cud be a wheel bearing if it is a rumbling vibrate or even wheels need balancing is it the engine itself vibrating a little bit more info if poss wud be gud m8