His father, Meyer Löw Schomberg (1690–1761), was a German-Jewish doctor and settled in England c. 1720 and set up a flourishing practice in Fenchurch Street, London.

Joining the Navy in 1743 as a midshipman under Captain Edward Pratten on HMS Suffolk (70 guns), he passed his examination for lieutenant on 3 December 1747, entering the sloop Hornet on 11 December and transferring from there to Speedwell, another sloop, in the West Indies in spring 1750.

This ship, however, was only in the home fleet and on the Bay of Biscay station and he was put on half pay again from June to October 1756.

There he was appointed to the Essex, with that ship taking part in the 1764 reduction of Belle Île, under Commodore Augustus Keppel and then serving in the Brest and Biscay fleet until the peace.

In August 1763, when peace came, he married Arabella Susannah Chalmers, only child of the Revd James Chalmers and Arabella, sister and heiress of Sir Edmond Alleyne, baronet, of Hatfield Peverel, perhaps with Hogarth's portrait commissioned and completed in time for the wedding.