postgresql suddenly stopped working "incomplete startup packet error"

I've searched and read a lot about these kind of errors, but none of them solved my question. Why does this error happens all of a sudden ? could this to be a problem of memory on the server ? (I checked the disk space and ram though like but it didn't seem to have problems related to this) Postgresql version 8.3 OS CentOs CLST LOG: incomplete startup packet CLST LOG: received fast shutdown request CLST LOG: aborting any active transactions CLST FATAL: terminating connection due to administrator command CLST LOG: autovacuum launcher shutting down CLST FATAL: terminating connection due to administrator command (HERE COMES A LOT OF THESE ERROR LIKE 15 times) CLST LOG: shut down CLST FATAL: the database system is shutting down" CLST LOG: the database system was shut down on 2021-12-29 11:12:00 CLST CLST LOG: autovacuum launcher started CLST LOG: Database system is ready to accept connections then it started to work just fine