Overheating Issues

[1209er]

Im having issues with my truck it is a 2004 ram 1500 5.7. Every time i start it once it reaches normal running temp it will overheat for about 5 min then it will sudenly drop back to normal running temp. I believe it is a faulty thermostat. I got home the other day just as the temp had dropped to normal running temp. I decided to take a look under the hood and noticed that my return hose to radiator was hot while outgoing hose was barely warming up also the radiator was hot on the return side and just warming up on the other side wich leads me to belive the coolant had just started flowing threw the system wich brings me back to the thermostat . Any input do you think that could be the issue. Any feedback welcome.