If this is a 1ph induction motor it is a very good sign that maybe the start capacitor requires replacing, it is very important that an induction motor reaches base or normal load speed within a couple of seconds or less.
At switch on an induction motor load has very little inductance and appears to the AC supply as a transformer with a shorted turn secondary, if it does not obtain proper rpm within this time, burn-out can occur, or if lucky, the breaker will pop.
On some recent equipment I purchased that had R.O.C. made motors, the same symptoms appeared, R.O.C. motors are notorious for poor design and capacitor failure.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.