Nissan Maxima Trouble

Hey everyone, I'm new to AF & was hoping to get some help. My 95 Nissan Maxima has been intermittently cutting off while I've been driving for the past week. It also cuts off while idling. I went to take it to the shop & today it wouldn't even crank. I had to tow it to the shop. I don't think its the battery (alarm, lights, radio & everything electric still works). All it does is click when you try to crank it. Any ideas?

Thanks!