Should I Drive or take train to cinque terra

If you have a rental car, you might park it in La Spezia and take a train in. Or, you can take the train from Pisa to La Spezia and a local train into Cinque Terra. Either way since it's just for 1 day.

You can park at the La Spezia station parking garage.
Or if you want you can drive to Riomaggiore and park at the two story parking structure in Riomaggiore itself. I usually park in Riomaggiore. Just be aware that the last mile leading down to the village is very narrow, although it is a two way road, so you must be confident to know how to negotiate a car in narrow spaces, or you risk to scrape the walls with your side mirrors.

Where are you going after Cinque Terre? If it's back to Volterra, you can also train from Cecina which is closer to Volterra and should have easier parking. Why Riomaggiore? If you've not been to the CT before, you might find other villages more evocative. How comfortable are you driving in Italy? That round trip makes for a long day of driving - best for sharing with two drivers. Getting from Volterra to the autostrada involves many curves and numerous settled areas. Doing much of it by train would be my preference.

The first thing to do when considering a drive somewhere is to look up the route on www.viamichelin.com [not google maps], rounding up to the next half hour or hour at a minimum.

You are looking at 2.5 hours minimum. Parking in La Spezia you would then have a train trip, time getting to the station ahead of that.

Drive only when/where it’s impossible to get to by train. You’ll save $$ and headaches.