Welcome to 2CarPros.
It very possibly could be a shift solenoid. However, make sure the fluid is clean and full and there are no leaks allowing line pressure to lower.
As far as the solenoid, I attached a picture below of the valve body and highlighted the two shift solenoids. However, before I would go to the trouble of replacing them, you really should have the computer scanned to determine if there are any diagnostic trouble codes related to the transmission. That could indicate the exact cause.
Please keep in mind, the low end scanners aren't usually able to read codes other than engine codes, so you may need to have it done.
Let me know if you scan and find codes. That would be really helpful.
Wednesday, September 11th, 2019 AT 5:28 PM