sometimes my car won't go into gear. I have to turn off car , put it in park and they put it in drive. Is this the transmission or a clutch

To confirm - you have an automatic transmission, correct? A "clutch problem" -- this transmission has clutches and shift solenoids and a valve body and bands - and it certainly could be an internal mechanical problem that is occurring. However, it could also be an electronically controlled transmission issue as well. Hands on diagnostic testing using proper equipment hooked up to monitor and even command transmission operation is needed. Without this, you'll only be guessing. Check fluid level and condition for sure -- that is one thing you can do otherwise, to start with.