Tachometer not working
 

Recently, I have new fault. When start the car, tachometer or working fine for few moments and then freezes and after that drops to 0. But engine is working fine and can’t feel any difference.

Also when the engine is hot, car is hard to start, there it cranking but nothing more. After roughly 20 minutes car starts fine.
Where to start? And maybe someone has had similar problems

Thanks