whoppa

hey guys, when unarming my car hopping in turning the key to the reds then attempting to fire somtimes it doesnt crank at all, it just stays at the reds and has a 5 second delay then sometimes it cranks over and all is fine. but somtimes it isnt 5 seconds, its longer. so i take the key out and try again and somtimes it'll fire straight away. but today it did not i had to jump out of the car arm my car by locking it, unarm it get in and it cranked first go.. could this be a lose wire in the barrel or starter motor??? due to this happening only 4 out of 10 times if i take it to the auto elec to test it knowing my luck it wont happen at all.
as this car is now for sale i dont want this happening to the new buyer when is he looking to buy it...
chris