1998 Durango 5.2L

My blower motor cuts in and out quite a bit now. If I turn off the ignition for a short period of time, let's say, to pump gas, and crank it up again...it will take a good 5 minutes for the blower motor to turn on. On long trips for about 30 minutes or more, the blower motor slowly dies. After it dies, I wait a good 10 minutes and it will start up again. Even when its on high, it's still relatively weak. I read a lot of posts saying that the blower motor resistor could cause this problem. I switched them out, but I still have the same problem. I'm guessing it's the blower motor, but I want to make sure before I start tearing apart my dash. Any help would be greatly appreciated.