Phone turns off?

[ajaffair]

Sometimes my phone will just turn off and when i turn it back on (when i can, and it takes forever i think it might be longer than when i restart the phone normally) the battery will be at a much lower point than before it crashed, and today after it shut off a second time the battery life was at a higher point than it was before it crashed the first time. It also turned off a third time today and this time i couldn't get it to turn back on or charge. But eventually after talking the battery out (for a second time) and putting it back in after a few minuets it finally turned on and is charging fine. There has been two occasions where it has failed to get passed the little htc green and white load up screen and i had to take out the battery and put it back in to get it to completely load up. Should i get a new battery, and will it work? What battery should i get/what is the best that will work for my phone?