Car shakes for no reason even driving, maybe fuel filter? plz help

[brad`]

hey lately in the last few days while im driving or even stoped at lights my car will shake enuff that everyone in the car can notice the vibration,

the first couple of times i just put it down to the ecu being stupid but then i noticed that when the "shakes" happen the Revs dont go up or down they stay the same,

i checked the T/b this arvo and it is clean no build up, i got it cleaned about 4months ago as well as getting a new IAC.

also checked the spark plug leads as well as the spark plugs them self they are all tight and none were loose, (not sure if any need replacing tho)

i checked the battery terminals as well the Positve had white corrosion build up so i cleaned it off and rechecked all the connections took the car for a drive and same issue still occurs

i cant seem to work out what is causing the "shakes", all tho my car is over due for a service, the oil is in between light and dark brown so no TOO bad still needs changing, air filter is new, hasnt had a Tune up since i have owned the car just over a year now, not sure when the last one was done the car just clicked over to 140,000k

any help would be good

cheers
brad`