Lower your dbcache. You've set your dbcache to 2000 which would essentially use your entire ram that your RPi has, and I don't think Bitcoin Core will automatically lowers it. The likely case is that some of the UTXOs gets dumped onto the ram fairly quickly and exhausted it. Delete the dbcache configuration or put a more conservative estimate, say 100MB and observe your processes. You can increase it slightly if it doesn't consume all your ram.