Sometimes it is a bunch of little things that add up over time. If it were me I would do the following:

Open up rx case and blow out any dust/dirt accumulated (as mentioned before)
brush the sensor port on the esc with a soft dry brush to get any accumulation away from there
check the connector from esc to rx for any cuts/melted insulator/broken plastic/loose connector
resolder all of your motor and battery leads - hot iron, nice and shiny
reset all the transmitter settings to neutral
re bind the rx and tx
reset the neutral/throttle/brake parameters from esc/tx

Good luck.