Bipolar Green Cheek?

I have a Cinnamon Green Cheek Conure named Henry.
Some days he is an absolute angel. Calm, well behaved, sweet... Other days he seems to have woken up on the wrong side of the perch and by that I mean he's extra bitey.
Is there any explanation for this? There doesn't seem to be any difference in how we handle him from day to day.

Here is my biggest question though as it is becoming quite a problem.
Thankfully my mother loves Henry as well and enjoys spending time with him. My Summer will be ending soon and I'll be going back to college. My school is nearby so I can visit over the weekend from time to time and see him and since my mom also likes him I don't have to worry about him not getting the attention he needs. Sometimes I really think my mom is his favorite haha. BUT! All of the sudden Henry has started biting my mom's ears. If she were to pick him up or hold him he would probably be fine, in fact he has been. I covered my mom's ears the other day and he sat on her without a problem. He was really sweet actually. Why is he suddenly on a mission to bite her ears (sometimes to the extent of bleeding.)?
My mom does yell quite loudly when he does it. I always tell her not to, as I've read quite a bit about how that can encourage them (like it's a game or something) to do it more, yet she always just says, "I can't help it. It's just a reaction." I just don't know what to do... Naturally we put him away right when it happens.
I usually have my ears covered by hair when he's out so I'm not sure if he'd bite mine as well... I don't really want to test that theory... but does anyone have any suggestions? I'd hate to have to go to school before the problem was fixed because then he'd never get let out of his cage while I was away.

Look into pressure training. Until then he should not be allowed on anyone shoulder. It's a privilege, not a right. Trust must be earned. Good luck.

Our gcc, Foofany can have her moods. The trick is figuring out what can do it.

Make sure they are on a good diet. Yes, it does not just effect health, but their mood as well.

Is Henry sleeping well? Foofany can be like a child and if a lot is going on at night she will fight us about going to sleep, she doesn't want to miss out on the fun ya know. If she doesn't get her beauty sleep at night she will be ugly the next day. This is usually when we get bipolar conure behavior.

other things that effect Foo-fear of new stuff. Now this usually puts her in a sweet mood, cause she wants to be one with us so we can protect her from whatever the evil thing is in the house-like that toy that is red. (how could we!)

She likes to her scritches a lot, and if she is getting in new feathers and we don't help with the scratching, someone needs to be punished. If said scratches are done wrong-well..someone needs to be punished for that too.

Sometimes she likes to groom us, and sometimes that grooming can hurt. I'm not sure I'd calling it biting..more like pinching. Ears can get that easily.

Ways that I handle it-if she is in a pinchy mood she isn't sitting on my shoulder. If she is being angry and biting, then I just put her in house or play yard. We've also taught her the word gentle. So a reminder of gentle usually works unless she's having a tantrum.

The humans in the house are my husband, my daughter and myself and she expects all of us to be part of her daily life. If one of us is unavailable for an extended time she will punish that one when they get back. My husband had to do 12 hour shifts for a two week period and was not seeing her during that time. It took months before she didn't just go crazy yelling at him and biting him. My daughter goes through this every time she goes back to school as well-usually takes her a week or two to forgive her about the schedule change.

I don't know how long you've had Henry, but a lot of it just takes time to be able to read them and their moods so you can avoid situations before they escalate.

I feel like this is a really common thing for GCC's. It almost is part of their charm. All joking aside, my advice is to have patience and just understand that you are dealing with a temperamental and bipolar 2year old child with ADHD, a knife, and wings. They have their awesome fun qualities, but we have to understand they can't be perfect. Work through the hard times with lots of training and give rewards for good behaviour. Birds respond really well to positive reinforcement.