Intermittent Engine Starting problem?

So, when you say struggles to start, do you mean crank over? (starter) or the engine cranks over okay but does not run? We need more information to help you. If it is hard starting then this guide can help, but being a diesel the #1 problem with these cars is the fuel filter/water separator needs to be replaced, has that been done recently?

https://www.2carpros.com/articles/engine-cranks-excessively-before-starting

If you can upload a short video of the engine cranking over it will help me, see what's going on.