Severe muscle spasms will make you feel "locked up" the muscles will be very hard to the touch and not pliable as normal.
I had spasms so bad at one point that I could not turn my head or flex much at all with upper body. ( all neck/shoulders, upper back locked up ) and my chest "vibrated" is best I can describe it.. expert chiro /PT should eb able to tell if that is the case. MDs should if they actually touch & feel for it , but often they don't even do that basic thing..