Okay - the back story

I have a 2yr old female corn snake. She is in a 55gal with 4 hides, high temp is 85F and low is 75F. She has been kept in this manner for 1yr now without any issue. She eats once weekly and sheds every 6-8wks.

She had also never shown any aggression towards me before now.

The last two weeks have proven interesting, though. Twice now she has bitten me. Both times have been while I was trying to retrieve her from her cage, and both times have been the day before or the day of feeding.

Any ideas what has caused this change in her? Like I said, nothing about my routine or set up has changed in almost a year, so I think it unlikely that something is bothering her. Is this snake PMS? Do I need to increase her prey size or frequency?

Thanks in advance for the help!