Burn-out. Been there. Typically, it starts out for me because I bowl the winter season, then bowl summer, then next winter I start to experience burn-out. What I would normally do is not bowl in the summer.
This year they were offering a sport type of league during the summer so I joined for the challenge. So far I havent experienced any problems with being 'up' for the leagues but that could change. What I have been doing is trying to find something to get my interest up for each week.
That has been trying out some different bowling balls to check the reactions on the various league conditions and trying out some of Ron C's bowling tips like the Finger Dancing tip to keep me focused on the shot. Finding someone at the center, preferably on your own team, to talk about bowling and the current lane transitions has also been helpful to me and may work for you.
If all else fails, take a break for a couple of weeks and see if the desire re-appears.
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I am the SGT Schultz of bowling.
"I know nothing!"