“We're upping the pressure as Amazon has so far given no sign of understanding and is endangering employees' health for company profits,” Orhan Akman, a representative for service workers' union Verdi, said in a statement.
Local worker representatives estimated that up to 450 employees joined the strike at an Amazon logistics centre in the western town of Rheinberg.
Walkouts were also planned to last into Tuesday in Werne, Leipzig, Bad Hersfeld and Koblenz, some accompanied by protests.
Akman highlighted a recent coronavirus outbreak in Bad Hersfeld with “30 to 40 colleagues infected” as one pressing reason for the labour conflict.
As well as improved measures to protect workers' health, the union wants Amazon to sign on to regional wage agreements covering retail and e-commerce stores — a battle Verdi has been waging for years.
Opposition Greens party co-leader Annalena Baerbock backed the strike, calling for “fair wages, dignified working conditions and above all a collective bargaining agreement” at Amazon.
But the company said that it already pays wages “at the upper end of the scale for comparable work”, adding that it offers “chances for many people to develop their careers and above all a safe working environment”.
It highlighted $4 billion of spending worldwide on measures to protect employees and customers from coronavirus infection, from hand disinfectant to protective masks.
The strike will have “no influence on maintaining deliveries, as the vast majority of employees are working as normal,” Amazon said.
Amazon says it employs around 13,000 full-time workers at its 13 German logistics centres, with thousands more seasonal workers.