Rolling/Movement under driver's side floor

2000 BMW csi with 113,000 miles. When I turn right or left I can feel something rolling under my left foot as it sits flat on the floor. Not every turn, but very often. At first I thought something, maybe a water bottle was under my seat.
I recently had 4 new tires installed, and this wasn’t happening before. Wondering what this could be and if it sounds dangerous.

Loose balancing weight on a wheel?

Does this car have heater ducts that blow out on the passenger’s feet in the back seat? If so, I would suspect that something from the back seat floor rolled in to the heater duct and ended up in the low spot beneath your foot.

If the movement is beneath the car rather than in the cabin, then it is most likely a worn-out rear bushing on the front control arm. On a 2000 with those miles, those control arm bushings are due for replacement.

It’s a dumb idea, but an easy one to check. See if those lug nuts are tight. I’ve had work done that required a tire removed and got a similar feeling from someone not paying due diligence to a basic step.

Thank you for your answers! I will see what my guy says, and I’ll sound really smart when I throw out your ideas like they’re my own. Hmmm…with the car, he knows me too well. Trouble too often.
Thanks!

Look for a golf ball in the heater duct under the seat.