Hard Start Kit will help. Most of us use SUPCO SPP6e.
Will also help an older compressor as noted above. Their resistance goes up as they age. This can cause premature failure in the start circuit. A H/S kit, perhaps along with a new Run Capacitor, can help it start.
If the RUN capacitor is failing, Compressor will have trouble starting and draw more current. Consistent with symptom you describe.
Seven Years is NOT old for a Rooftop RV A/C or its compressor. Unless maybe it's been run on low voltage (say below 110) for a lot of that time.
ME? I'd
1. Pull Shroud and Wiring Cover. Inspect Capacitor(s). Look for swelling and leakage.
2. Read the value off the Run Capacitor. Probably around 10-45 MFD and 370 or 440 volt. If it's combined with Run for the Fan (around 5-7 MFD) either get a replacement that covers both in one "can" OR get a single capacitor. You'll a jumper for the Common terminals
3. SAFETY FIRST - Shut A/C Breaker OFF, and then short across the capacitor terminals to be sure they're discharged before you touch them.
4. See if it starts using a full-voltage AC supply (115 volts or better, heavy duty RV power cable)
5. If it doesn't start and HAS a Hard Start on it (will include a plastic capacitor around 88-108 MFD), disconnect and try again.
6. If starts, my suggestion would be replace Compressor Hard Start and Run Capacitors, for Compressor AND Fan. You can get the parts on Amazon, at Appliance Parts stores, etc. NO Need to pay "RV price."
7. Remove sheet metal over the Evaporator Coil (at front of unit) and clean the coils. Drip oil on the Fan Shaft where it enters that Motor.
8. Call it GOOD. I can't promise the compressor is NOT bad, but the odds and our experiences here indicate that compressor failure is far less common than capacitors, dirt, fan motors, and refrigerant leaks.
