Sometimes my heat on my 08 charger gets cold at an idle. Once I start driving it will get hot. Could this be heater core or thermostat?
no , low on coolant most likely
Check the fluid level first. Then check radiator cap and then thermostat. Sometimes having air in the system can cause this system, but mostly low fluid levels. However, as I understand it this has been a known problem with Chargers with the 3.5L high output V6 and the 6.1L Hemi, which have an oil cooler installed, with the oil cooler plugging up and causing heat loss at idle. If a simple fix doesn't do it for you, might have to talk to someone at the dealer.
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