I have noticed my Inoculator activates itself randomly without any obvious purpose (no matter if my characters health is low or high).
First time I noticed that was in a Hunt mission and I thought my VIP was using it but then I recognized this was happening in other missions, too. If this is meant to happen, I have no idea what makes it happen.
It's kind of sad when I have no charges left, when I need them.
(I hope this wasn't asked before, since I didn't find anything about that topic.)