Volkswagen Repair: 2002 VW Beetle Hot start problem, coolant temp, fuel mixture

Question
My 2002 Beetle has an intermittent problem. About once per week it won't start when warm, like when returning to the car after a 10 or 20 minute stop at the store. It turns over until the battery dies, then just clicks. But if I let it sit for 1 to 1-1/2 hours so it's cold, then it starts right up. It always starts when cold. The car has 47,516 miles on it, and the codes from the mechanic are 1296 P118 Coolant Temp. Sensor, P1570 Immobilizer Start blocked, and PO 302, 304 random misfire. The mechanic says the coolant temp. sensor wouldn't be the cause, and recommended I try the backup key, but the problem remains. What about a relay? Is heating the relay with a hair dryer a reasonable way to replicate the problem? Thank You!

Answer
Scott,
 Sorry for the delay, I was out sick.

 Sounds exactly like the cooling temp or CHT sensor.  If these are bad, the computer always thinks the car is "cold".  Then when the car is really warmed up, it enriches the fuel mixture too much, making it very hard to re-start.

Rick