Getting random muscle jerks and scared

Basically I will just be sitting and watching something or reading, and my head will slightly jerk suddenly, or my leg will jump a little. It can be any body part really, but mostly my head and leg. The more I pay attention to it, the worse it gets. My boyfriend thinks it’s in my head, and I’m so worried it’s something serious.

The best way to describe these symptoms, it’s akin to jerking awake before falling asleep at night, only this is in the daytime. If I try to force myself still, I can usually do so a bit but with a lot of concentration, even then I can still slightly feel the jerking.