When I'm overwhelmed or stressed, I freeze up, stare blankly, and sometimes rock back and forth?

Not on it's own no. However others may follow so watch to see where it's going. It's a type of self soothing that stressed people use for different reasons. How long do they last for? 5-10 Min's isn't too worrying but 4-5 hours is more alarming. If it's most of the day then it's a sign of mental illness almost definitely. I've seen people who were on older type antipsychotics do that for hours and most of them were schizophrenics. It was very sad. What is going on in your head during these times do you think or just shut down?

Hope you can cure this