Ultrafast fiber lasers based on Mamyshev oscillators (MOs) are very attractive for their high performances and environmental stability. However, high-performance MOs are usually started by external seed pulses from complicated and expensive ultrafast laser sources. We demonstrate an all-fiber erbium-doped MO started by a compact and low-cost nanosecond passively Q-switched laser for the first time. The starting dynamics of this MO are experimentally investigated with broadened spectra of the seed pulses and dispersive Fourier transform technique. The success rate for starting the MO with a seed pulse train seeding can reach nearly 100%. The oscillator can deliver stable ultrafast pulses with repetition rate of 4.86 MHz, energy of 14.5 nJ and 10-dB bandwidth of 103 nm, proving the ability of the method in supporting high-performance pulse generation from a MO. This work provides a cost-effective and reliable solution to start erbium-doped MOs, which has the potential to be extended to other wavelengths.