The lawnmower seems to be 'chugging' as if it is not allowing the correct amount of fuel to be consumed, in order for the lawnmower to run on full power. Its asif there is a choke holding back the fuel-power. It continually dies and cuts out.
If the lawnmower is chugging it sounds like you need to look at the air and fuel filter or try some redox in the tank that may flush through thr blockage.