First thing I would check are your connections.
Check the ground wire from the battery to the engine and then check the
postive cable from the battery to the starter.

Make sure they are tight and look for any signs of wear,
such as bare wires etc.

It could be that you have a bad battery, solenoid, or even the starter.

Start with the simple stuff first like the connections.

the click/Brrr that you hear is the starter solenoid (on the starter motor).
When the battery voltage is too low to properly run the starter solenoid and
starter, you get that buzzing sound.

If the battery is more than four years old, think about replacing it in any
event. Sometimes you get lucky and can pull off the battery cables, clean
the terminals and your're back in business. Corrosion on the battery
terminals can cause those problems.

You can also measure the battery voltage (simple voltmeters are now very
inexpensive). Battery voltage for a properly charged battery with engine off
should be about 12V. With the engine running the voltage should be almost
14V. This voltage should be pretty constant regardless of engine speed or
load (turn on headlamps and blower)

hope that points you in the right direction - Oppie