Compressor not kicking on right away

[Unit]

Hey guys, not sure if this is a low refrigerant issue or something more involved. Have a 2004 Ranger in which the air always worked great. Was on vacation for 2 weeks and the truck just sat idle. Upon returning, when i used the ac, the compressor would not kick on right away. Once it does kick on, the air works great. Problem is that it's getting worse and now will take up to 30 minutes before the compressor kicks on. Any ideas? Thanks in advance!