Last winter my Odyssey would turn over fine but would not start after it sat for awhile during cold weather (20 degrees or less). After I put a heater under the hood for about 30 minutes it would start. Any ideas what is wrong?

 

My guess would be spark plugs or spark plug wires.

 

no, it would most likely be the coil packs, once you heat them up their resistance will go up enough to generate current to the plugs.

 

Oops, correction, i forgot the new odyssey's had coil packs!!