For the past few days, my left big toe has been tingling on and off. what could cause this?

Could be a : Pinched nerve in your back, a tight shoe, a hallux limitis, anterior tarsal tunnel syndrome. I would start ruling those out...

Altered State.: The cause of the tingling is always the same. The electrical impulse moving along the nerve is being scrambled or disrupted. These altered or incomplete impulses are being felt as tingling. The most common cause of the tingling in the big toe, especially the medial side, is a developing bunion. Shoe pressure on the enlarging bone presses on the nerve and the altered impulse feels like tingling.