I feel vibration in the drivers seat when idling at stop. Is this an engine mount problem?
Very likely, yes, this could be an engine mount problem. Could also be a mis-firing cylinder, too. Is the check engine light on?
No. The drivers seat only vibrates when I stop at a light or stop sign. No vibrations when driving.
So no CEL? Then engine mounts.
Does this have to be repaired immediately? There is no vibration when driving
I would want to get a good diagnostic done so I know exactly what the problem is, then decide if it can be deferred.
Would there be more vibration in the car when driving if it was the engine mount?
Agree with @BillRussell Have it looked at and decide.
Trying to avoid costly diagnostic
Do you feel lucky?
I can’t see the car nor feel the vibration. In the vacuum of the internet, I’m going to tell you to have ti checked out. whether or not you do it is up to you. The engine won’t fall out but it could break your exhaust pipe or damage wiring or other things if it is bad enough.