2006 Nissan Sentra 1.8S will start only after 2-3 cranks

You may have a leak in your rear-main seal. a leak in the rear-main will sling oil all around underneath the auto. Your starter is in the direct line of fire of the oil leaking and being slung. I have the same make and model. It started on my car at about 75,000 miles and, other than having to crank it 2-3 times before it starts, ran fine. I decided at 225,000 miles(current mileage is 265,500) that cranking it 3-4 times was excessive and decided to replace the starter. It only took about an hour to change it out but I searched for it for 4 hours before I watched a few you-tube videos(very helpful). It is on the lower backside of the engine, above CV axles. A serious pain in the ASS to get to! Anyway, after I changed my starter it fired up on first crank every time, until more oil got slung up on it. My advice, check for lower engine oil leaks, like rear-main, and repair that before replacing your starter. Hope this helps and good luck.