Is there a trial plan for Microsoft 365 similar to what we get in Office 365 ?

For Microsoft 365 Business, a trial offer is on it's way (from the FAQ):

Is there a Microsoft 365 Business trial I may use to evaluate the offer?

A Microsoft 365 Business trial will be available later this year both for direct customers and for CSPs.

I'd contact sales if you're interested and see what they say, there is a link on the front page of the product page though it's only available during business hours in each territory. By the way, Microsoft 365 Business was in Public Preview but became GA recently.

For Microsoft 365 Enterprise I can't see any indication of a trial but contacting sales through the above method, via the sales link on the product page, would be the way to go or reaching out to a Microsoft partner.  Keep an eye out on the documentation as well, in case it becomes clearer.