The chugging and hard start is usually leaking injectors. These are wear items, and should be changed.

The car typically will heat up in to the 100 ish degrees at which point your electric fans should kick in and bring you back down in to the 80's- 90's. You can (should) do a coolant flush, and new thermostat. Just keep in mind the temp fluctuations are somewhat normal.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2