No it's not possible at the moment because there's a law in place called the "Atomgesetz" which would have to be changed first and there is no support in the populace for that. Five of the six power plants that have been shutdown in the past few years could technically be restarted in 1-2 years but the 2000 personnel required are not available anymore, and won't come back if there's no perspective for next couple of years. This perspective does not exist in Germany at the moment, since the plan is to move to renewables and green hydrogen power plants.

Sources: https://www.handelsblatt.com/unternehmen/energie/energie-forderungen-aus-bayern-lassen-sich-stillgelegte-atomkraftwerke-einfach-wieder-hochfahren/28550996.html

https://www.zdf.de/nachrichten/wissen/atomkraft-deutschland-debatte-wiedereinstieg-klimaziele-100.html