@Johannes has a good point here, if there should be a malfunction withe the vol. button, it might explain why your phone often boots into the recovery.
How did you leave the recovery? Did you select the option reboot system there? And did this reboot selection also bring you back into the recovery?
There are a (very) few reports here in the forum of malfunctioning volume buttons, and I also earlier had some issues with the vol. button, as the vol. down function often did not work. These problems though are gone I think since version 1.3.6, though there was nothing in the release notes that seems to be connected with the issue (also it wasn’t a known bug afaik).
Maybe, when you’re back in Android, you could (and with an unstable device anyway should) make a complete backup of all your data, and see if a factory reset or a hard reset solves the issue? That’s what I would try (that is, I would maybe flash the whole system after backing up the data).