Engine stalling at idle?

My escalade recently began stalling when it is idling. The problem first started about a month ago. I was stopped at a red light and the car stalled. When I went to start the vehicle it turned over several times before actually starting. This occured a couple more times over the next few days. I also noticed that even without stalling the vehicle was sometimes, but not always, turning over more before actually starting. I put some fuel injector cleaner in my tank and filled up thinking maybe something got into my gas tank (accidentally or intentionally) and gummed up my injectors. This actually did help for a couple of weeks, then about a week ago the problem started again. The stalling only occurs when the vehicle is idling, either in gear or in park. When the vehicle is started back up after stalling it always turns over numerous times (10-20) before it actually starts. Also, once it stats back up a message comes on that says "service stabilitrak". Lastly, sometimes the check engine light also comes on. I had it checked and the code given was "crank shaft positioning sensor." Not sure it this code is actually causing the problem or if it happened as a result of the vehicle stalling, which is being caused by something else. Any help is GREATLY apprectiated!