It could be an app you installed (or combination of apps) , you should check what you have installed lately
example :
I've recently installed WhatsApp in my MileStone , but it was interfering with both RealPlayer beta & Google Maps (even though I don't start them , they start all together even when i kill one of them) which caused my phone to reboot at least 10 times a day & kill the battery in 1 hour , but when I uninstalled RealPlayer everything went back to normal
I hope that helps