Can I resign before I am dismissed?

I’ve just found myself in a situation where I’ve been suspended pending a disciplinary hearing next week.

I’m 100% certain I will be getting dismissed for Gross Misconduct.

Can I resign before I am dismissed? Will this affect any references in the future if I wanted to get another job in the same sector.

Also I have a company car, when would this need to be given back? I’ve been with the company nearly five years.

If I resign will I need to hand the car straight back or can I have it until the end of my notice.

Any help would be much appreciated