Suggest you take a look at all your electronic connections first....make sure everything is connected solidly.
Do your best to seperate any "signal " wires from "power"wires.
Example: Make sure a servo wire is seperated from the battery power wires.
Also ,when did you clean your motor last? Clean motor and check condition of brushes.
take a look at your receiver antennae wire..make sure its in good condition.
Hope this helps.