Check for dirt or dust in the connector. If possible try another wall charger and cable.
You can also try a reboot of your iPad. Press and hold the Home and Sleep buttons simultaneously ignoring the red slider until the Apple logo appears. Let go of the buttons and let the iPad restart. See if that fixes your problem.
Thanks Ralph. although it didn't directly solve my issue, your tips were helpful.
I blew into the port (old school Nintendo games style ), then connected it to an outlet. It still beeped on and off.
I moved to several different outlets and tried them all. It still beeped on and off.
I restarted the iPad, then connected it to a wall again. It still beeped on and off.
BUT...the most recent time, instead of quitting and unplugging it after 4 beeps (like I did for the past 48 hrs), I decided to wait it out and see what happened. After about 8 beeps, it stopped beeping and is now showing it is charging.
I'm more worried now that it is a problem with the long-term "health" of the iPad. For example, this never happened before, and I'm pretty sure it's not supposed to. Beeping once to tell you its connected and charging is the norm, so why the heck does mine beep 8 times before starting up? I'll probably troubleshoot some more in a bit (as in unplugging and replugging it in to see if it'll beep just once like it's supposed to or 8 times like it just did)...but I think I'll wait til it's fully charged first!
The quickest way (and really the only way) to charge your iPad is with the included 10W USB Power Adapter. iPad will also charge, although more slowly, when attached to a computer with a high-power USB port (many recent Mac computers) or with an iPhone Power Adapter (5W). When attached to a computer via a standard USB port (most PCs or older Mac computers) iPad will charge very slowly (but iPad indicates not charging). Make sure your computer is on while charging iPad via USB. If iPad is connected to a computer that’s turned off or is in sleep or standby mode, the iPad battery will continue to drain.
Apple recommends that once a month you let the iPad fully discharge & then recharge to 100%.
How to Calibrate Your Mac, iPhone, or iPad Battery
At this link http://www.tomshardware.com/reviews/galaxy-tab-android-tablet,3014-11.html , tests show that the iPad 2 battery (25 watt-hours) will charge to 90% in 3 hours 1 minute. It will charge to 100% in 4 hours 2 minutes. The new iPad has a larger capacity battery (42 watt-hours), so using the 10W charger will obviously take longer. If you are using your iPad while charging, it will take even longer. It's best to turn your new iPad OFF and charge over night. Also look at The iPad's charging challenge explained http://www.macworld.com/article/1150356/ipadcharging.html
Also, if you have a 3rd generation iPad, look at
Apple: iPad Battery Nothing to Get Charged Up About
Apple Explains New iPad's Continued Charging Beyond 100% Battery Level
New iPad Takes Much Longer to Charge Than iPad 2
Apple Batteries - iPad http://www.apple.com/batteries/ipad.html
Extend iPad Battery Life (Look at pjl123 comment)
New iPad Slow to Recharge, Barely Charges During Use
Tips About Charging for New iPad 3
Prolong battery lifespan for iPad / iPad 2 / iPad 3: charging tips