SQL Server OpenRowSet and OpenQuery queries hangs

We currently run SQL Server 2014 Standard (SP2) in a sandbox environment. It’s used mainly for BI purposes, and runs scheduled jobs, using data sources from linked Oracle servers, and a few CSV files.

About 1-2 per week, very sporadically/at random, the ability to execute very basic SELECT statements using OPENQUERY (Oracle linked servers) or OPENROWSET (CSV files) (which normally takes seconds/seconds), just processes endlessly. I’ve checked Hard drive space on the server, and that’s definitely not the culprit. The Log files are also set to clear overnight.

The only solution has been to hard reboot the server.

Are there diagnostics I should run/things to look out for? Trying to prevent this, rather than fix every single time.

Thanks!