Audi Repair: Audi A4 3.0 hard starting and erratic idle., coolant temp, engine coolant

Question
I own a 2003 Audi A4 3.0 V6 Quattro.  When I start my car about half the time it starts fine but sometimes it takes 2 or 3 tries.  Also when i put it in park it idles erratically.  It goes up and down between about 600 and 800 rpm quickly.  But when it's in drive it stops.  I took it to a reputable repair shop and they said it could be the temp sensor.  Also the check engine light has not come on yet.  Any ideas?

Answer
hello
I will start with checking the faults first, sometimes the light will not come on. It may be ECT sensor ( engine coolant temp sensor) but I will try to clean and adapt throttle plate. sometimes the is so much dirt on the plate and idle will jump like crazy.
good luck                 Greg