Usually means a health concern. Don't use lightly to describe minor worries or excitement. After running up the stairs, he felt palpitations and decided to see a doctor.
Pro Tip 2/3
Not Always Serious
Can describe temporary situations like a reaction to caffeine, not just severe illness. Caffeine sometimes gives me heart palpitations.
Pro Tip 3/3
Stress Connection
Often related to stress or anxiety situations, indicative of a body's reaction. Final exams always give me palpitations.