Pounding" sound in the back of my neck -- sounds like waves crashing (but once a second). doesn't hurt, happens about 1-2x a day for ~5-10m. problem?

CheckRelationToPulse: Given reported timing, this could relate to your pulse & blood flow. Unusual: might reflect a problem yet might be something you sense occasionally which most people ignore. If I am very still & especially in a quiet location, i can sense the pulse/blood flow in my neck, hear it in my ears, etc. I also understand the anatomy & physiology of human bodies fairly will & am not worried but reassured.

Short head pain: Stabbing headaches may be a trigeminal autonomic cephalgias. See your local neurologist for further evaluation as there are secondary causes for short lived multiple times a day headaches, such as posterior fossa tumors or pituitary tumors. Also neck pathology involving arteries to the brain can occur causing this type of headache. Hope this helps.

Need neurologist: You need a neurologist to check you for vascular bruits ( abnormal flow sound) that could be emanating from as far away as your heart or as close as your neck or brain. The neurologist will initiate the work-up and have you see a cardiologist if necessary . You are young for arterial blockage but anyone can have a heart valve murmur. An arterio- venous malformation inside the skull should be ruled out with appropriate tests.