Your unit outside is 10 years old, and has never been cleaned, the odds are in the 99% range that condenser
coil is dirty. It should be cleaned, after that we can go from there.
A dirty coil *looks* clean, the dirt however is lodged deep between the fins where it blocks air flow needed to keep it cool, when that happens the unit goes off on its high pressure cut out switch.
You can buy the foaming coil cleaner at Home Depot or Lowes, you need at least 2 cans. The chances are in the 80% range that cleaning the coil will resolve the problem.
After that you can look for a one inch diameter hole in the cabinet somewhere where around the electrical wire connects. If you see that, there is a red button inside that you can push that will start the unit... that is the high pressure safety cut out reset switch.
Let me know how all of that goes, we can proceed from there as needed without a time limit, unless you choose to rate my ongoing advices negatively, that will close the question. There are 6 or 8 other things we can look into if needed. You will need a multi meter to assist me in that.
We are on the honor system here. Please remember to rate my service before you leave today. It is how I earn a living, and does not increase your charges. If you need anything else, just let me know. You can continue asking follow-up questions within your agreed on limit at no additional cost.