2000 Ram Van 3500

I have a 2000 dodge ram van 3500,with about 240,000 miles. When I start driving the van cold, the transmission will function intermittently (goes into neutral) until it warms up. Once it warms up, it functions fine.
Any suggestions?

Is the fluid full? If not fill it and see if the issue goes away. If it's full than do a fluid/filter change and make sure both bands get adjusted then.