1997 Chevy Silverado left turn signal doesn't flash after a

When I first start out driving, my turn signals work perfectly. After a few minutes of driving, when I turn my left signal the left turn signal audibly can be heard but stops flashing. My right signal remains perfect. I had one of those big, square fuses for my blinker fuse and it felt very hot to the touch. I took it to a local shop that replaced the flasher - they thought that after driving a while the flasher was heating up and would stop working. After replacing the flasher, both signals worked perfect for the half hour I used it. On the second day it worked good for 15 minutes, but then again my left signal quit working just before I got home. The fuse felt warm, but not hot. I don't think it's the flasher this time, but is it more likely to be the turn signal flasher relay or the turn signal switch or could it be a grounding problem- which to check first and what is the course of action? Thanks.