Traffic in Bulgaria

Well it depends quite a alot on the city you're living in. If a smaller one - then there are no traffick jams, no waiting in the car etc ... However, if in a big city, especially Sofia, things are quite different.
For Sofia (and probably Plovdiv, Varna, Bourgas, Rousse, Stara Zagora) rush hours are between 7.30 and 9.30 AM, 11.30 AM and 2.30 PM, 5.00 PM and 7.00 PM.
I don't adwise on driving a car through the city center during these time intervals.
Parking is actually quite possible, excluding the top center area and costs 2.00 BGN/per hour in Blue Zone and 1.00 BGN in Green Zone areas(for Sofia). You can pay by SMS which is quite convenient.

I'd recommend against driving in Sofia, if at all possible. It's not so much the heavy traffic, although there is that, but also just the way people drive. It's awful, as is the smog that results from all the people driving. The public transport system -- metro + trams + buses -- is good and blankets the city. The Moovit app works well for travel planning. And if you can't get there that way, taxis are abundant and affordable.