Pressing ctrl_s on the terminal will cause it to look like it’s frozen. To unlock it, press ctrl_q.

ctrl_s sends a XOFF signal. This is part of Software flow control. XOFF notifies the process or device sending data that the input buffer is full and it shouldn’t send any more data.

References

• https://superuser.com/questions/1390977/pressing-ctrl-s-by-mistake-while-using-vim