FIRST!
j/k
In other vehicles i have owned these symptoms you've explained have been indication that the AC needs to be charged aka low on r134.
The cheapest 1st step to finding out is getting a can at autozone that has a gauge on it so you can recharge it and tell for certain. If that doesn't fix the problem, you could have a failing AC Compressor. Simply buying the r134 and recharging it will be a good bet in finding out if it simply needed charged or if its something else. I mean, if you charge it and it fixes it, you are out nothing. If you charge it and the problem persist, you are out 20bucs and know its something more serious- and maybe something more serious you don't care to have repaired