With no trauma...
Many causes of abnormal bleeding problem (coagulopathy): could relate to anything affecting platelets
medication (rx or otc such as aspirin
), bone marrow
disorders, rapid destruction of platelets in spleen), one of many types hemophilia
Clotting is very complex: blood tests first (some unisual); if cause not clear: refer to hematologist. Often, spontaneous bruises less than 2cm turn out ok, c doc.