A much more definitive way is to just hook up to a scanner and monitor the rpm of the crank sensor while cranking.   Starter fluid will work, but also have the potential to cause damage.  

If you open the air filter box and spray some quick start that will tell you if it's a fuel problem otherwise it could be a stuck crank sensor issue. just a thought

Id get some contact cleaner spray it and and spin the dial a bit. I've had cd players before that just needed a clean on the dial and would do strange things like you described before the cleaning 

“Fate chooses your relatives, you choose your friends.” Jacques Delille - poet  

Anyone know the cheapest place to get the Stabilus brand of lift supports? I believe it's 1617MX and I'm in the U.S.