Sudden full body "twitch" and scabs on neck

My new chinchilla will be scratching her neck and then all of a sudden have a fit and she shakes like a dog (but about a million times faster). It' just for a second but she jumps right after she does it (jump is also a lighting speed). Is this a common behavior?

She seems to be scratching around her neck more than anywhere else. She let me pet her and I felt some small scabs around her neck. Not very many, about the size of a pin head. The rest of her body looks/feels fine, she's eating, drinking, pooing, and peeing just fine. They are on both sides of her neck. Could she have scratched herself when itching?? Allergies? Has anyone else seen this?

I have her on aspen bedding. Her owner passed away two days ago and I took her in. Don't know anything about her past, her age, etc.

Thanks!