leosaurus

i have a 1999 cherokee 5 speed 2.5L,the past few mornings it cranks over and doesnt start.my aftermarket tach moves from zero when cranking.i have been able to get it started after several attempts of just cranking.usually takes about 10-20 minutes.when it starts it idles fine and runs normal and starts fine the rest of the day.the check engine light comes on and the only code is for oxygen sensor.would a oxygen sensor keep it from starting easilly?i have read other posts where people say crank position sensor or tps.im lost and cant wait 20 minutes to start it every day any help is appreciated.