Music of string quartets is not always quiet, and can often be extremely challenging emotionally and intellectually (as in the string quartets of Shostakovich, for example). But, to answer you inquiry, some quartets that will match what you describe include the following:
J. Haydn, String Quartets from his Opus 17, 33 or 54.
Mozart, String Quartet in A, K464
Bridge, String Quartet 3
Arriaga, any of his three String Quartets
Debussy, String Quartet in g, op10
Delius, String Quartet
Wikmanson, String Quartet in e, op1, no2
Good luck in your explorations.
J. Haydn, String Quartets from his Opus 17, 33 or 54.
Mozart, String Quartet in A, K464
Bridge, String Quartet 3
Arriaga, any of his three String Quartets
Debussy, String Quartet in g, op10
Delius, String Quartet
Wikmanson, String Quartet in e, op1, no2
Good luck in your explorations.