...1) check the battery. An old wornout battery can do this a lot.
2) I've had a switch/ignition cyliner issue (for about 4 years) where if you wiggle the key a bit it starts every time. The shop suggested I needed a "new or rebuilt starter" at that time... Needless to say the car has been starting for the last 4 years so I didn't follow their advi$e.
Cheers!