I have 3 beeps on startup too
here are some things I know about it
if you get into the habit of putting the handbrake off before you switch on the ignition you may well see the handbrake light flash once in time with the first beep
also there is a small plastic button/nipple on top of the brake fluid reservoir just behind the filler cap, if you press it quite hard it fools the car into thinking the fluid is low and you get the same 3 beeps and one flash of the handbrake light (providing the handbrake is off)
so far I have found that if you start the engine immediately (don't stop the key half way) you don't seem to get the beeps
I hope this helps people