It appears your system may not have enough memory. This step often requires 24-64 GB of RAM (sometimes more, sometimes less) depending on the reference database size, and the run settings. More is explained here.
It depends on the size of the reference database. For example, SILVA requires substantially more memory resources than GreenGenes, some custom databases require significantly more. Some custom databases can require close to 128 GB RAM.
How big is your database?
Have you tried reducing the number of jobs, and/or tried a machine with more RAM, as suggested in the post I linked? The more threads you use, in this case, the more RAM you'll require. So, reducing the number of threads may help.
Okay this might be a useful piece of information. What version of QIIME 2 are you running? What operating system? How did you construct your classifier?
If setting --p-n-jobs 1 does not work, can you send me a private message with links to your NCBI_16S_classifier.qza and representative_sequences.qza files via Dropbox or similar service? I'd like to test this out on my end, and make sure that it is not an issue with the files and/or your computer setup, or something else.